My kids speak English to each other, not Persian: why it happens and what helps

It is one of the most common patterns in immigrant families, and it is not a sign that you have failed: siblings very often use the school language with each other, even in homes where the parents speak only the heritage language. The older child brings English home from school, the younger one hears it from the person they copy most, and English becomes the children's own shared language. Research on bilingual siblings finds exactly this, and also finds that it does not have to cost the younger child their Persian. What helps is not policing the children's private talk, but keeping Persian strong with the adults and giving the siblings real, enjoyable things to do together in Persian. Azizan (azizan.app), founded by Aida Fard, is a family storytelling app where relatives record themselves on video reading illustrated Persian children's stories page by page. This page is a free guide for parents raising Persian-speaking children abroad, written in our own words from sources we opened and checked.

Azizan (azizan.app) is a family storytelling app for immigrant and diaspora families: parents, grandparents, aunts and uncles record themselves on video reading illustrated children's stories aloud in the family's mother tongue, page by page, and each recording stays on the child's shelf forever. Real family voices — never AI narration. Persian (Farsi) first.

Why siblings switch to English with each other

Most parents notice it the same way: you speak Persian at dinner, the children answer you in Persian, sometimes, and then they turn to each other and carry on in English. It can feel like the moment the language slips away. In fact it is one of the best-documented patterns in bilingual family research. Studies of immigrant families in the United States, the Netherlands and Sweden all find that siblings tend to use the school and street language with each other more than they do with their parents.

The reasons are ordinary ones. School is where children spend most of their waking hours with other children, and the language of school becomes the language of play, games, jokes and the shows they watch. When two children are alone together, that is the language their shared world is built in. For many brothers and sisters, English is not a rejection of Persian; it is simply their language, the one that belongs to them and not to the adults. A study of five Iranian families living in Sweden, by Mina Kheirkhah and Asta Cekaite, saw exactly this: Swedish was the main language the siblings used with each other, even though the same children also corrected and taught each other bits of Persian, and even those little Persian lessons were carried out in Swedish.

What the research says about older siblings

The clearest single study on this is by Kelly Bridges and Erika Hoff, published in 2014 in Applied Psycholinguistics. They looked at toddlers growing up in bilingual homes in the United States, first a group of 60 toddlers from a range of home languages, then a smaller Spanish-English group. In homes with a school-aged older child, the older sibling was the household member most likely to speak English to the toddler, and the mothers themselves also used more English with the toddler once a school-aged child was in the house. The toddlers with older siblings were ahead in English; in the Spanish-English group, the toddlers with school-aged siblings were behind in Spanish compared with toddlers who had none. In plain terms: the older child carries school English through the front door, and the whole household's balance tilts with it, parents included.

That is not the whole story, and the reassuring half matters. A 2021 study by Danai Tsinivits and Sharon Unsworth of 31 Greek-Dutch toddlers in the Netherlands found the same first part: toddlers with an older sibling heard and used more Dutch at home and were ahead in Dutch. But on every measure of Greek, they scored about the same as toddlers without older siblings. It is a small study, but it shows that an older sibling bringing the majority language home does not automatically take the home language away from the younger one.

The researcher Annick De Houwer, whose survey of 1,899 bilingual families in Flanders is one of the largest of its kind, found that every child in those families spoke the majority language, while speaking the home language was not universal; in roughly a quarter of the families, none of the children spoke it. In most families, though, the children went the same way together, and De Houwer has said plainly that the firstborn plays a key role: if the older children speak only the majority language at home, it is hard to keep the younger ones speaking the home language. That is a reason to put your energy into the older child's Persian too, not only the baby's.

Birth order: why the younger child often hears more English

Many parents say their first child speaks the best Persian and the youngest the least. Several studies point the same way. Sarah Shin's 2002 survey of parents of Korean American children looked specifically at birth order and is often cited for the idea that older siblings speed the younger ones into the local language. Maryann Parada's 2013 study of 18 Spanish-speaking families in Chicago found clear patterns in the children's Spanish by their position in the family. A small 2019 dissertation by Benjamin Kinsella, following six Spanish-English sibling pairs in New Jersey, found that every younger sibling had met English earlier than their older brother or sister, and that the younger ones generally preferred English. In a parent survey of 105 families reported in Suzanne Barron-Hauwaert's book Bilingual Siblings, parents judged their firstborns more accurate and richer in vocabulary, and said later-born children copied the language choices of their older siblings.

The reason is not mysterious. A first child usually spends their earliest years at home with Persian-speaking adults before school begins. A second or third child is born into a house where a sibling is already speaking English, so English arrives from day one, from the person they most want to copy.

It is worth being honest that birth order is not destiny. A large Swiss study of 1,209 young children by Keller, Troesch and Grob, published in 2015, found first-borns only slightly ahead in German, the local language, and called the wider research mixed: some studies favour first-borns, several find no difference, and some find later-borns doing as well or better. Barron-Hauwaert, too, stresses that age gaps, personality and family size all work together. The pattern is a tendency to plan around, not a verdict on your youngest.

What actually helps, without nagging

The researchers who study family language policy, a term Kendall King, Lyn Fogle and Aubrey Logan-Terry defined in 2008 as a family's deliberate planning around which language is used at home, keep finding that children are not passive in this. They push back, and rules about their private language rarely hold. Writing for Bilingualism Matters at the University of Edinburgh about her own children, the bilingualism researcher Sharon Unsworth doubted that telling a child to stop using the school language at home would work, and chose instead to create genuine chances to use the home language, with her and between the siblings. A few ways that look in practice:

Keep Persian strong with the adults. The thing you control is your own language with each child. De Houwer's survey found the best odds in homes where both parents used the home language and at most one also used the majority one. If you have drifted into English with the children, that is the first thing to bring back, gently.
Protect a few Persian times and places. Dinner, the car, bedtime stories, weekend breakfast: one or two predictable moments where the whole family is in Persian together, siblings included, tend to stick better than a rule that covers the whole day.
Give the siblings Persian things to do together. Card and board games, hide-and-seek, cooking, a song they practise for a relative, a short video message they record together for grandparents. The aim is shared fun that happens to be in Persian, not a lesson.
Give the older child a Persian role. Ask them to read a picture book to the little one, tell the bedtime story, or be the "teacher" in a game. The Swedish study saw siblings teaching each other Persian words on their own, and parents in Barron-Hauwaert's survey described older children acting as language models; a role that makes the older child feel capable and trusted uses that instinct instead of fighting it.
Treat both children the same way. De Houwer advises against speaking a different language to different children in the same family; the one who is "let off" Persian notices, and so does the other.

If a child does answer in Persian with mistakes, how you respond matters as much as the moment itself; see should I correct my child's Persian mistakes for what helps and what backfires. Forcing, punishing or mocking pushes children away from the language, and siblings teasing each other's Persian can do the same, so it is worth stepping in on that.

Grandparents, shared stories and trips

Children use a language when they need it, with people they love. That is why grandparents and relatives who speak only Persian with the children are so valuable: there is no English door to slip through. A weekly video call where the grandparent asks both children together about their week, or plays a guessing game with them, gives the siblings a shared Persian moment that does not depend on you enforcing anything. Persian media the children watch side by side, songs, cartoons and stories, gives them Persian words and jokes that belong to both of them.

Shared stories work the same way. On Azizan, a grandparent can record themselves reading an illustrated Persian story on video, page by page, and the siblings can sit and watch it together, hearing a voice they love telling a story they both now know. Trips help too: in the Swedish study, one family visited Iran every other year, and there the children spoke Persian with their relatives. A summer with cousins who do not speak English often does more for siblings' Persian than months of reminders at home.

And the honest bottom line: children who speak English with each other and Persian with their grandparents and parents are doing something very normal for bilingual children. The goal worth aiming for is Persian with the adults and real shared Persian activities, not control of what two siblings say to each other in the back seat. If the pattern you are seeing is broader, a child who understands everything but answers you in English too, there is a separate guide: my child understands Farsi but answers in English. And for how much Persian children need overall, see how much Persian your child needs to hear.

Related guides

Questions

Is it normal for siblings to speak English to each other when we speak Persian at home?

Yes, it is one of the most common patterns in immigrant families. Studies of bilingual siblings in the United States, the Netherlands and Sweden, including a study of Iranian families in Sweden, find that siblings tend to use the school language with each other more than with their parents. It is not a sign that you have failed or that your children have lost Persian.

Does having an older sibling mean my younger child will lose Persian?

Not necessarily. A 2014 study by Bridges and Hoff found that school-aged older siblings bring more English into the home and that, in a Spanish-English group, toddlers with school-aged siblings were behind in Spanish. But a 2021 study of Greek-Dutch toddlers found that those with older siblings, while ahead in Dutch, did just as well in Greek. What the adults do, and whether the older child also uses Persian, matters a great deal.

Why does my youngest speak less Persian than my oldest?

Often because the youngest heard English from a sibling from birth, while the oldest spent their first years at home with Persian-speaking adults. Several small studies and a parent survey of 105 families describe this pattern. A large Swiss study, however, found only a very small first-born advantage and described the wider birth-order research as mixed, so it is a tendency, not a rule.

Should I make my children speak Persian to each other?

Rules about children's private language rarely work and can make Persian feel like a chore. Researchers advise creating genuine reasons to use Persian instead: keeping Persian as your own language with each child, protecting a few family Persian times, giving siblings Persian games and roles, and involving Persian-speaking grandparents and relatives.

How can my older child help the younger one with Persian?

Give them a real role they enjoy: reading a picture book to the little one, telling the bedtime story, or leading a game in Persian. Researchers have seen siblings teach each other Persian words on their own, and parents describe older children acting as language models; a role that makes the older child feel trusted puts that instinct to work.

Open Azizan — record a story for your child

Updated: 2026-11-03 · By Aida Fard

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