do first cousins have the same dna
Sorry, something has gone wrong. Trending Now. Answers. Best Answer: First cousins only share an average of 12.5% of their DNA, so yes, they do share some DNA, and yes, your child would also have some of the same DNA, but not enough to make it a problem. The way it works is your child is 50% you and 50% his other parent. Your 50% is half each from your parents, so your child is 25% of each grandparent. First cousins have a grandparent in common, but the other DNA is not shared.