Recent developments in assisted reproductive technology (ART) – the use of third parties in the process of fertilization and pregnancy, and cryopreservation of human sperm, ova and human embryos – have contested many previously unchallenged paradigms related to parenthood. Currently, the thesis that a person is created by the physical consummation of two living parents of the opposite sex, is no longer as simple and clear cut. Undoubtedly, these changes affect social norms, including the legal systems of individual states which take divergent stances on the above-mentioned issues. For example, in their approach to filiation relations of a child born through ART and how his/her parents’ data are entered on the child’s birth certificate. Intensified migration movements of Poles to the USA and an increased number of cross-border (Polish and American) relationships have resulted in a growing frequency of foreign birth certificates appearing in Poland. Though incompatible with the Polish law, such certificates provide grounds for certain claims to be filed since vital records are documents of particular importance in every legal order, and in succession proceedings they are of fundamental value. Thus, a question arises as to the viewpoint of Polish law in regard to American birth certificates which do not comply with the rules in force in Poland regarding the filiation indicated therein. Can a child inherit by operation of law from people of the same sex indicated in his/her birth certificate issued abroad and can he/she inherit from all the parents named in such a certificate even if there are more than two of them? Does a child conceived several years after the death of his/her father, whose data feature on the American birth certificate, have a right to inherit from him in Poland? This article attempts to answer these questions.