The farther out the branches go on your family tree, the more relationship terms you need to include. You may have started by gathering information about the family members with whom you share consanguinity. These people would be your parents, siblings, and other relatives whom you are “blood related” to. Once you start adding family who are not consanguineous with you, things become more detailed.
No matter what you may think of your in-laws they are a part of your family tree. An in-law is a person who you are not genetically related to, but become related to as a result of marriage. This means that the mother of your spouse is your mother-in-law, and the father of your spouse is your father-in-law. Your spouse will call your parents mother-in-law and father-in-law. If you have siblings, they become your spouse’s brother-in-law or sister-in-law. Your spouse’s siblings become your sister-in-law or brother-in-law. You have no genetic relationship to your in-laws.
Half siblings are people who you do share some genetics with, but not all. If your father or mother had children with someone who was not your father or mother, those children are your half siblings. You share a parent with these children. Maybe you have the same mother, but different fathers, for example. You may have a half-brother or a half-sister.
Step relations are people who are part of your family, but you do not share any genetic background with them. If you have a step sibling, this person does not have the same mother or the same father as you do. Often, step siblings become part of a family when a person who has a child marries another person who also has a child. The children become each other’s step brother or step sister. The newly married parents become a step mother or step father to the child of their spouse.
Sometimes, cousins will be described as “removed” No, this does not mean that this person has been thrown out of the family. Instead, the word “removed” is used to signify that you are in a different generation than your cousin. In a family tree, your first cousin once removed would appear one generation away from where you are at. Twice removed means that you and this cousin are two generations away from each other.