This article examines the Kansas Supreme Court case of K.M.H., 169 P.3d 1025 (Kan. 2007) within the context of an increasing body of US case law that addresses the legal status of known sperm donors vis-à-vis their biological children born to women who are not in heterosexual marriages. The article begins with an explanation of US parentage law and then reviews and synthesizes the cases leading up to the K.M.H. decision. The article then details the four different opinions in the K.M.H. case, and, in particular, lays out the discussion of the constitutional challenges to the Kansas sperm donor statute. Next the article discusses how the previous known sperm donor cases impacted the sperm donor’s arguments in K.M.H., and how these cases failed to support his claim for parental rights. The article continues with a review of two more decisions, issued after the K.M.H. case, incorporating these cases into the evolving trends discerned in the recent court decisions. The article concludes by summarizing K.M.H.’s position within that evolution.