Cal. PROB § 21374

(a) A person who is “related by blood or affinity” to a specified person means any of the following persons: (1) A spouse or domestic partner of the specified person. (2) A relative within a specified degree of kinship to the specified person or within a specified degree of kinship to the spouse or domestic partner of the specified person. (3) The spouse or domestic partner of a person described in paragraph (2). (b) For the purposes of this section, “spouse or domestic partner” includes a predeceased spouse or predeceased domestic partner. (c) In determining a relationship under this section, Sections 6406 and 6407, and Chapter 2 (commencing with Section 6450) of Part 2 of Division 6, are applicable.