What happens when identical twins marry identical twins and have children?

They would therefore be first cousins by law, but siblings by nature.

It is so rare that very little research has been conducted on it. 

This phenomenon occurs when identical twins have children with another set of identical twins within nine months.

The story of a quaternary family.

They got married in Twinsburg, Ohio, in August 2018  wearing identical dresses, and even had identical wedding rings for the ceremony.

They broke the news of their pregnancies in August 2020 with a Baywatch-themed photoshoot.

The chance of you having a quaternary twin is 1 in 24666666.6667!