A collection of fascinating pictures from across the globe shared online prove just how strong genes really are.

The snaps, shared to viral site BrightSide, document the incredible similarities decades of families share. 

In one captivating case a set of twin brothers in China married twin sisters, and both gave birth to twins. 

Elsewhere  a baby from Atlanta was born with the exact same birthmark as her mother - a tuft of grey hair at the front of her centre parting.