Two Bobs

If two pairs of identical twins have kids, will the children have the same DNA?

Hypothetically, say that Bob and Tom are identical twins. And Jessica and Marie are identical twins. If Jessica marries Bob, and Marie marries Tom, and each pair has kids of their own, will the kids (I guess they would be cousins) have the same DNA? And if so, wouldn't that mean that if Marie and Tom had two kids, the two kids would have the same DNA?

Though it is possible, it is very very very unlikely. That is because the gametes of the parents, the egg and the sperm, each carry a different combination of genetic information. One sperm may have a dominant gene for a certain trait, another sperm may have a recessive gene for the same trait. Same thing with the eggs. If Bob and Jessica has a kid, and Tom and Marie has a kid, that really is no different than me and my wife having two kids. My second kid won't be exactly the same as my first because even though my wife and I have the exact same genetic code as we did when we had my first child, the random combinations of my genes and her genes will produce a completely different child.

So the chances of the two couples in your example have kids that are the same are no more than a single couple having two kids that are the same.

My Two Bob's Worth - Community Council