Our results indicate that there is an effect of birth order on divorce risk. It is evident from our estimations that single children run a lower risk of dissolving their marriages. Marriages between two first-borns are the most unstable relationships, whereas marriages between two only children are the most stable.

Does birth order really affect personality?

Birth order does not appear to influence personality in adults, according to several ambitious studies published in the past few years. This new wave of research relied on larger data sets and more robust statistical methods than earlier reports that claimed to find a relationship between birth order and personality.