A child born to a spouse prior to the marriage to the other spouse who has not legally adopted the child. If the child is legally adopted by the non-biological parent, that child is no longer a stepchild and is treated the same as a biological child. If a will leaves property to my children state law (some following the Uniform Probate Code) will determine whether a stepchild qualifies as a child when used generally in a will and whether it means only biological children.