BIG brothers and sisters have long been said to torment their younger counterparts - but new Sheffield University research shows they can actually increase their chances of living longer lives.
But later they soon show themselves to be a nuisance, as the more older same-sex siblings you have in young adulthood, the less likely you are to marry and have children of your own.
The study aimed to investigate the effects of siblings at different stages of life on longevity and reproductive success.
Experts from the university’s Department of Animal and Plant Sciences analysed church records of about 20,000 Finnish people born between 1750 to 1900.
During childhood, a boy with no elder siblings had only on average a 68 per cent chance of surviving to age 15, whereas a boy with four elder sisters or brothers had a probability of surviving of 75 per cent. But during adulthood, each living same-sex sibling decreased the probability of ever having children.
Investigator Aïda Nitsch said: “These results demonstrate family members often both cooperate and compete, and benefits and costs of having elder siblings may vary across life and between siblings.”