CAL. FAM CODE § 7611 : California Code - Section 7611

A man is presumed to be the natural father of a child if he meets the conditions provided in Chapter 1 (commencing with Section 7540) or Chapter 3 (commencing with Section 7570) of Part 2 or in any of the following subdivisions:

(a) He and the child's natural mother are or have been married to each other and the child is born during the marriage, or within 300 days after the marriage is terminated by death, annulment, declaration of invalidity, or divorce, or after a judgment of separation is entered by a court.

(b) Before the child's birth, he and the child's natural mother have attempted to marry each other by a marriage solemnized in apparent compliance with law, although the attempted marriage is or could be declared invalid, and either of the following is true:

(1) If the attempted marriage could be declared invalid only by a court, the child is born during the attempted marriage, or within 300 days after its termination by death, annulment, declaration of invalidity, or divorce.

(2) If the attempted marriage is invalid without a court order, the child is born within 300 days after the termination of cohabitation.

(c) After the child's birth, he and the child's natural mother have married, or attempted to marry, each other by a marriage solemnized in apparent compliance with law, although the attempted marriage is or could be declared invalid, and either of the following is true:

(1) With his consent, he is named as the child's father on the child's birth certificate.

(2) He is obligated to support the child under a written voluntary promise or by court order.

(d) He receives the child into his home and openly holds out the child as his natural child.

(e) If the child was born and resides in a nation with which the United States engages in an Orderly Departure Program or successor program, he acknowledges that he is the child's father in a declaration under penalty of perjury, as specified in Section 2015.5 of the Code of Civil Procedure. This subdivision shall remain in effect only until January 1, 1997, and on that date shall become inoperative.

(f) The child is in utero after the death of the decedent and the conditions set forth in Section 249.5 of the Probate Code are satisfied.