“Being the daughter of a twin mother, from an early age I have found twins to be a source of amusement and perplexity,” Sandrine Kerfante writes in the introduction to the photography book she edited, Two of a Kind. “When I was a young child, it was really amazing to discover the perfect double of my mum.”

For Kerfante, “the perfect double” doesn’t have to mean matching DNA; her book was adapted from her blog, twin-niwt, “a collection of twin-like images from different artists.”

“Twin-like” can mean sisters who mimic each other’s behaviors, an important part of socialization for children. It can mean friends who feel so close they wish they were blood-related, so they dress up in matching knee-highs. It can mean two, spindly Cyprus trees that happened to grow together to a matching height. Or two metal chairs shoved together, their legs interlocked.