What Documents Do You Need to Prove Family Relationship?

A mother:

Submit a copy of your birth certificate showing your name and your mother's name.

A father:

Submit a copy of your birth certificate showing the names of both parents. Also give a copy of your parents' marriage certificate establishing that your father was married to your mother before you were born, and copies of documents showing that any prior marriages of either your father or mother were legally terminated. If you are filing for a stepparent or adoptive parent, or if you are filing for your father and were not legitimated before your 18th birthday.

A child born out of wedlock and you are the father:

If the child was not legitimated before reaching 18 years old, you must file your petition with copies of evidence that a bona fide parent-child relationship existed between the father and the child before the child reached 21 years. This may include evidence that the father lived with the child, supported him or her, or otherwise showed continuing parental interest in the child's welfare     

Stepparent/Stepchild:

If your petition is based on a stepparent-stepchild relationship, you must file your petition with a copy of the marriage certificate of the stepparent to the child's natural parent showing that the marriage occurred before the child's 18th birthday, copies of documents showing that any prior marriages were
legally terminated and a copy of the stepchild's birth certificate.             

Adoptive parent or adopted child:

If you and the person you are filing for are related by adoption, you must submit a copy of the adoption decree(s) showing that the adoption took place before the child turned 16 years old. If you adopted the sibling of a child you already adopted,
you must submit a copy of the adoption decree(s) showing that the adoption of the sibling occurred before that child's
18th birthday.

In either case, you must also submit copies of evidence that each child was in the legal custody of and resided with the parent(s) who adopted him or her for at least 2 years before or after adoption. Legal custody may only be granted by a court or recognized government entity and is usually granted at the time the adoption is finalized.
However, if legal custody is granted by a court or recognized government agency prior to the adoption, that
time may count toward fulfilling the 2-year legal custody requirement.