Once a person is adopted (either as a child or as an adult) all inheritance rights of the biological family of the decedent are terminated.
In the past, prior to the legalization of same-sex marriage, many partners in same-sex relationships adopted each other, to create a legal recognition of the relationship. Adoption also happens often during second marriages, when one biological parent has either died or abandoned the child. Adoption also frequently happens now by grandparents adopting their own grandchildren, whom they are raising full time, because the biological parents are either in jail or addicted to drugs.
When adoption happens, all past biological relationship is terminated for the purpose of inheritance. The adopted person becomes part of the family tree of their adoptive family, standing to inherit just like a biological child of that family would. The original biological family is not entitled to inherit anything in case of intestacy.
There is, however, a way of overcoming this result: if an adult wants to provide for their original biological family, they can write a Will naming the specific people they want to leave money to. As each person has (almost) complete freedom to dispose of their assets as they please, one can leave money to one's original biological family.
Please contact Sverdlov Law PLLC at 212-709-8112 or ksverdlov@sverdlovlaw.com if you need help with inheritance, probate, or administration matters.