"What does your boy cook?"
Translation:Что готовит ваш мальчик?
Hello again! I find a similar case. For the english sentence "What does your boy cook?", there are two possible answers: Что готовит твой мальчик? / Что готовит ваш мальчик?
I guess that is a clarification for the learners, because the english "you" ("your") has both singular and plural connotations. Thanks a lot!