How do you say

(a) What is your family like
(b) When is your birthday

in French?

b. Quand est votre anniversaire?

(a) Comment est votre famille? (that's if you are using the formal "vous" but if you are on a first-name basis, it's a peer or younger = Comment est ta famille?)

Sra (aka Mme)

To say "(a) What is your family like?" in French, you can say "Comment est ta famille ?"

To say "(b) When is your birthday?" in French, you can say "Quand est ton anniversaire ?"

Keep in mind that the translations provided here are informal. If you want to address someone politely or formally, you should use "votre" instead of "ta/ton" to show respect.