This paper provides evidence that daughters make people more left-wing. Having sons, by contrast, makes them more right-wing. Parents, politicians and voters are probably not aware of this phenomenon – nor are social scientists. The paper discusses its economic and evolutionary roots. It also speculates on where research might lead. The paper ends with a conjecture: left-wing individuals are people who come from families into which, over recent past generations, many females have been born.
I'm quite skeptical. For one thing, wouldn't this contradict the stylized fact that most people's political views are substantially fixed by their late teens?
For another, my wife and I are firm counterexamples.