Does your sister like eggs? here we mentioned "your" sister right? then why we can't use "do your sister"

'your sister' is singular subject so we use in this sentence 'Does' not 'Do'.

Really I can't understand you &your both words are same i mean singular so i,we,you,they- we use do only right then here why can't use do your sister.

"Your sister" is third person singular subject, so it's been used "does" here.

because in there is only one person who is asked for.