Who's the oldest child IN/OF your family?

[Jupiter]

Hi teachers,

Who's the oldest child in/on your family?

Which preposition is correct?

Thanks in advance

Jupiter

[Rosalisa]

Hi

If I don't get you wrong, you mean "Who's the oldest child in/of your family?" In this point, "in" is correctly used, but when you use "of", you should ask "Who's the oldest student/child of those students/children?"..........
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If you want to change the world, be one of the change.

[Jupiter]

Hi Rosalisa,

Thanks for your response. You did get me right.

I notice that you're from Cambodia too.
Can we get to know each other?

jupiter

[Rosalisa]

Hi Jupiter,

Nice to know you. Obviously, I'm from Cambodia too. Where particularly in Cambodia are you from?
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If you want to change the world, be one of the change.

[Jupiter]

Hi Lisa,

OK, I'm from its capital, Phnom Penh.
Nice to know you too.

Let's contact privately

Jupiter