have the same DNA to contribute.
So for genetic purposes, it doesn’t matter which of the two identical twins actually fathers or mothers the child. They are the same.
Genetically, they all have the same parents. There will be random variations in similarity to any sibling, like I said before (38%-61%) but they will be somewhere in that range for their cousins as well as siblings.
AND are as likely to be as or more genetically similar to those cousins as to their own siblings.
To be clear, we’re taking about non-identical for all the children. But identical-twin dads that married the same pair of identical-twin moms, right?