A person’s first cousin once removed is their mother’s cousin. A once-removed relationship is the same relationship but separated by one generation. Once removed, a cousin’s child is likewise a first cousin once removed. The term “second cousins” is frequently mistaken with this.
The children of one’s parents’ cousins are known as second cousins. At least one great-grandparent is shared by second cousins. The younger generation’s great-grandparent is the older generation’s grandparent when they are first cousins once removed.
Although uncommon, a relationship known as double first cousins occurs when two brothers marry two sisters and produce offspring. The youngsters are first cousins twice removed and share both sets of grandparents.