Sorting Out Relation

Sometimes people, especially young people, aren't certain of how to describe their relation to someone else. It doesn't help that legal relation isn't always the same as genetic (blood) relation.  People can legally be siblings, but not be close genetic relatives, for example. Or two people can be genetic siblings but not legal relatives. Relation by blood/genetics is referred to as consanguinity and relation by marriage or law may be referred to as affinity.

Generally, the law recognizes that people are related through birth*, adoption, or marriage (or civil union or domestic partnership.)

I hope this provides clarity to people who are uncertain.



Cousins: This is explained in detail here, so I will just be brief and say that your parent's sibling's child is your first cousin. Your first cousin's child is your first cousin, once removed. Your child would be a second cousin to your first cousin, once removed. Also, your first cousin is your child's first cousin, once removed.



Full sibling: A brother or sister whose biological/genetic parents are the same as yours.

Half sibling: A brother or sister who shares one, not two, biological/genetic parents with you. Because people can have half-siblings, they can also have half-uncles, half-aunts, half-cousins, half-nieces, and half-nephews. For example, your parent has a half-brother. He would be your half-uncle (although many people choose to simply say "uncle".) Note that someone can have two half-siblings who are not closely related to each other genetically.


Adopted/Adoptive: When legal arrangements were made to become legally recognized family, which otherwise happens through marriage or birth*. For example, if your parents adopted an orphaned boy, he would be your adopted brother and would be legally as much your parents' child as you. Or you could both be adopted by the same parents. It isn't just minor children who are adopted. Adults have adopted other adults.


Stepsibling, Stepbrother, Stepsister, Stepparent, Stepmother, Stepfather, Stepchild, Stepson Stepdaughter: A relation through marriage and is usually someone who is not a close biological relative. Someone is your stepsibling/-brother/-sister because their parent married your parent. Your stepsibling is the child of your stepparent. Someone is your stepparent/-father/-mother because they married your parent. Someone is your stepchild/-son/-daughter because you married their parent. For some purposes in some places, some laws treat steprelations like biological/genetic or adoptive relations. Sometimes, a steprelation becomes an adoptive relation, such as when a stepparent adopts their stepchild.



In-law: Someone who is related to you by marriage or custom (but usually this person is not a steprelation) and may be recognized as such by law or socially. The parents of your spouse would be your mother-in-law or father-in-law. Your spouse's siblings would be your brother-in-law or sister-in-law.  Your sibling's spouse would also be your sister-in-law or brother-in-law. Your child's spouse would be your daughter-in-law or son-in-law.



People generally refer to other people by their closest relation. For example, if you married a second cousin, you would generally call them your spouse, not your second cousin, as spouses are legally next-of-kin and second cousins rarely are (all closer relations would have to be deceased). Or, if your parents adopted your cousin, it would be customary to call your cousin your sibling.


*The term "birth" is often used in place of "genetic" or "genetics" but it should be noted that:

1) Surrogate mothers often give birth to children to whom they have no close genetic relation, and they will not be the legal mother of that child.

2) Some women give birth to, and raise, and are the presumed and legal mother of children to whom they are not closely genetically related because the child was conceived using a donor egg or was a donated embryo.

3) In many places, parental designation (such as paternity) is automatically assigned under the law to a spouse of the woman who birthed the child even when the child has no close genetic relation to this "birth father/parent" because the child was a donated embryo or conceived by sperm donation, or sexual intercourse with someone outside the legal marriage, regardless of whether or not the sexual intercourse was something this spouse knew about.






More terms used frequently on this blog are explained here.