Paternity is legal fatherhood—and establishing it is one of the most important steps in the child support process. A man is generally presumed to be the father of children born to his wife during their marriage. The presumption of the husband’s paternity can be rebutted through court-ordered genetic testing. The circumstances under which paternity is presumed vary from state to state, and are usually included in a state’s statutes—often in the statutes grouped together and known as the family code.

In California, paternity, or legal fatherhood, is crucial in the child support process. Under California law, a man is presumed to be the father of a child if the child is born during his marriage to the mother. This presumption can be challenged in court, where genetic testing may be ordered to determine paternity. The conditions for presuming paternity are outlined in the California Family Code. These include the child being born during the marriage, the child being born within 300 days after the marriage ends, the man marrying or attempting to marry the mother after the birth, the man agreeing to be named on the birth certificate, or the man accepting the child into his home and openly acting as the father. If paternity is disputed, either party can request the court to order genetic testing. Establishing paternity is essential for determining child support obligations, custody, and visitation rights. It also grants the child legal rights and benefits, including inheritance rights and access to the father's medical history and health insurance.