According to the idea to extend the circle of statutory inheritors within the Polish Law it has been established to declare the testator’s spouse children legal successors. Such a solution seems to be in concordance with the rules of the family law like a stepfather’s or the stepmother’s obligation to pay alimony to stepchildren. Protection of affinity relation inter vivos seems to have wider scope because it comprises mutuality which has not been included in succession. The idea to make the testator’s spouse children legal successors can be accepted with approval, there arise doubts as to the rules adopted. The most doubtful is that the testator’s spouse children may become legal successor only if both their parents died before inheritance proceedings have started. Besides, there is no clear explanation of the understanding of the statements “the testator’s spouse children” and “dead on opening of the inheritance” with regard to the 934(1) rule of the Civil Code.