“Siblings share about 50% of their genes, so there is an evolutionary logic to investing and being interested in a siblings’ welfare, Caspi said. “What we don’t really know is the root cause, whether it is that happier people areless depressed people andare better able to formpositive relationships with siblings or having a great sibling relationship is helping people better cope with all the things that life throws at you.
“People seem to be healthier, happier and better adjusted - all of those things are related to having positive relationships with siblings, you know, and a lot of that comes from this idea that you can get support and help and validation from having someone close to you who shares a history and understands the world in a similar way to you,” Kramer said.
