Is it 'an aunt' or 'a aunt' ? same question for 'uncle'?
Do you understand generally how to decide whether "a" or "an" is appropriate?
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
People usually say "my uncle" or "her aunt."
There are plenty of occassions when using "a/an" for family members is natural.
She has a sister in Chicago.
I have an aunt who works there.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.