When the family relationship meets the criteria of U.S. immigration agencies in terms of when and how the link between parents and children or between husbands and wives was created.
Child is how U.S. immigration agencies refer to someone who has a valid link to a father and/or mother, who is unmarried, and who is 20 years old or younger.
Daughter is, for U.S. immigration agencies, someone who has a valid link to a father and/or mother and who is either 21 years old or older, or 20 years old or younger but married. If she is unmarried and 20 years old or younger, she is a child.
Son. For U.S. immigration agencies, a son is 21 years old or older. Otherwise, he is called a child. A son can have different links with his parents.
Sibling is a brother or sister. For U.S. immigration, siblings must establish that they share at least one common parent.
Spouse. A husband or a wife. For the purpose of U.S. immigration, the spouses must be legally married.
A father or mother. For the purpose of U.S. immigration, a parental relationship can be a biological relationship, a step-relationship, or an adopted relationship.
Common parent is how U.S. immigration agencies refer to someone who is the common father or the common mother of two siblings. Sharing one parent through a valid link makes two people siblings.
Derivative applicant is spouse and/or children of the applicant who are eligible to obtain a green card alongside the applicant. (also called “derivative beneficiaries”).
Biological relationship. One of the links for a qualifying family relationship. The birth mother can always claim a biological relationship with her son or daughter. Broadly speaking, the father has to be or have been legally married to the birth mother, or have formally legitimized his son or daughter to claim a biological relationship.
Step-relationship. One of the links for a qualifying family relationship. A stepparent / stepchild family relationship is immediately created by the legal marriage of the stepparent and the biological parent when the stepchild is 17 years old or younger.
Step-relationship immediacy. There is no need to show a close family unit for the purpose of U.S. immigration when a stepparent/stepchild relationship is involved. For instance, a U.S. citizen stepfather can sponsor his stepchild as an immediate relative as soon as he is legally married to the stepchild’s biological mother, even if he has never met the stepchild in person.
Adopted relationship is one of the links for a qualifying family relationship. It is created by the legal adoption of the adopted child by the adoptive parent before the adopted child turns 16 and by the physical and legal custody of the adopted child for at least two years.
Legitimization is the fact of placing a child born out of wedlock in the same legal position as a child born in wedlock. Note that for a legitimization to be valid under U.S. immigration rules, the child must be in the legal custody of the relevant parent or parents at the time.