This sounds like a shitpost but seriously how in the fuck did John and Jane bang two totally different people and end up creating the same fucking person
You know since this post has been on my dash a couple of times today and the origin of Dad is still a fandom debate, might as well apply some science to it.
B1 Dad is the uncle of B2 Dad, that means on average there should be 25% genetic similarity between them. However it can get as high as 32%. Given their similarity we can probably assume it is likely higher than not.
We are never shown or given any detail regarding Mr. Egbert or Mrs. Crocker. But given Nanna and Poppop grew up around the same place, it is entirely possible that their partners also came from the same place and perhaps are even related. If we assume Mr. Egbert and Mrs. Crocker happened to be siblings than that also makes the Dads cousins.
Cousins are on average 12.5% genetically similar, but for the Dads that would put them at a total of 37.% likely similarity (if combined with the average for aunt/uncles and niece/nephews). However cousins can get as high as 22% similar and if we combine that with the 32% high from early, it means the two Dads could be up to 55% genetically the same, even greater then the percentage of similarity between a parent and child.
Cheloneuniverse 