Estate of Cornelious (1984) 35 Cal.3d 461 remains good law. Under Probate Code 7540(a), a child is conclusively presumed to be issue of the man married to the child’s mother, so long as the two were cohabiting at the time of conception and of birth. Such a child is not allowed, at least for inheritance purposes, to prove that he or she is really the child of a different father. However, a finding that mother and her husband were cohabiting at the time of conception and birth is essential to the application of section 7540. Here, the trial court made no such finding, and so erred in granting summary judgment against B, who claimed he was decedent’s son and heir despite his mother being married to a different man at his conception and birth.