An aunt is a person who is the sister of a parent. Aunts are second-degree and share 25% genetic overlap when they are the full sister of one of the biological parents. Known alternate terms include Auntie or Aunty. A half-aunt is a half-sister of a parent and is a third-degree relative with 12.5% genetic overlap. An aunt-in-law is a wife of one's uncle, direct genetic overlap will typically be 0%, as this person entered the family through marriage and typically is not a blood relative. An aunt-in-law can also be an aunt of one's spouse. A co-aunt-in-law is a wife of one's uncle of one's spouse. A double-half-aunt is a daughter of a paternal grandmother with maternal grandfather, in other words, maternal half-sister of one's father and paternal half-sister of one's mother at the same time. A double-half-aunt also is a daughter of a maternal grandmother with paternal grandfather, in other words, paternal half-sister of one's father and maternal half-sister of one's mother at the same time.