New state-sanctioned family units headed by couples in committed relationships are on the rise. They include marriages encompassing same sex couples, civil unions, and domestic partnerships. These new family units can originate in state statutes or in judicial decisions. The pace of change is so fast that new units occasionally replace units only recently recognized, as when same sex marriages replace civil unions or domestic partnerships. U.S. Supreme Court precedents permit broad governmental discretion in sanctioning new families and in recognizing parentage therein. Yet such discretion is limited by constitutionally-recognized parental rights and interests when children are born of sex. At times states can and do deny parental status under law at birth to biological fathers. Differences in parentage laws will likely continue for some time. When same sex marriages, civil unions, or domestic partnerships are expanded or created, the new family units typically are deemed equal to, or the same as, longstanding opposite sex marriages. However, when there are children born of sex, equality and sameness are impossible. Same sex couples simply cannot produce children through intrafamily intercourse as can opposite sex couples. Yet, extrafamily intercourse by those in same sex, as well as opposite sex, families can produce children. Given the policies of equality and sameness, should all children conceived through adultery similarly be deemed born into sanctioned family units? That is, should there always operate a presumption of parentage as now typically operates for a husband in an opposite sex marriage? If so, are new written laws needed since the existing parentage presumptions for husbands usually require the possibility of genetic ties – an impossibility in same sex settings? Further, are there limits on any equality between same and opposite sex couples? Finally, are additional laws beyond parentage presumptions at birth needed for children born of sex to same sex couples? This article posits that explicit statutory presumptions are needed for children born to state-sanctioned same sex female couples although there cannot be genetic ties in both mates. Further, it proposes that current voluntary parentage acknowledgment processes, now operating for men who prompt children born of sex to married and unmarried women, be expanded to allow certain same sex male mates to become legal parents at birth, or sooner, to children born of sex into their family units.