My child's friend's mom has died and the children were wondering if their Mom's house (in her name only on deed) goes to their dad (who is on drugs) or would they share in the inheritance? They are all grown children. Thank you.

Did the mother have a will?

If there was no will, was the house acquired by the mother before or during the marriage?

(The questions can go on and on, and it's best if the parties directly involved are doing the asking.)

This site describes the CA laws of inheritance:
Dying Without a Will

As you can see, this matters only if there was no will. And, community property does have a bearing.