Before revision: Unless related by marriage, they are generally 25%DIF < related by blood if the aunt/uncle is a full sibling of one of the parents, or 12.5% if they are a half-sibling.
After revision: Unless related by marriage, they are 25%DIF < related by blood if the aunt/uncle is a full sibling of one of the parents, or 12.5% if they are a half-sibling.