CA Fam Code Section 3951

(a)

A parent is not bound to compensate the other parent, or a relative, for the voluntary support of the parent’s child, without an agreement for compensation.

(b)

A parent is not bound to compensate a stranger for the support of a child who has abandoned the parent without just cause.

(c)

Nothing in this section relieves a parent of the obligation to support a child during any period in which the state, county, or other governmental entity provides support for the child.