Take a look at the photo. Do these two look like identical twins? Well they aren’t. Not really. Well… sort of.
They are cousins but very unique cousins. Some people (who may or may not be experts in genetics) also claim they are full siblings (I may not agree with that).
In any case, they are very closely related. WebMD claims they are are quaternary twins, which is very rare.
Oh yes, they are both named Peter.
OK, I’ll let you figure out the relationship. It seems that their mothers, Sally and Chelsea, are identical twins. OK, that’s not so rare but here’s the second item in their relationship: Their fathers, Pedro and Peter, are ALSO identical twins!
According to Peter and Peter, ”Because our moms are also identical twin sisters, that actually makes us full siblings, not half-siblings.”
The fact that both men are named Peter is simply coincidence, the parents named the new babies without consulting with the other parents.
You can read more in an article by Emily Lefroy published in the New York Post at: https://nypost.com/2023/06/20/were-cousins-but-also-genetically-brothers-heres-how/.
OK, so how do you fill out a pedigree chart for these two?