British study finds link:
The more daughters there are in a household, the more likely the parents are to vote Labour or Liberal Democrat. In an unpublished paper that has been submitted to an economics journal, the pair declare: “This paper provides evidence that daughters make people more left wing. Having sons, by contrast, makes them more right wing.”
This doesn't explain ME, since I was a lefty long before my daughter came into my life. But I can see, as my daughter approaches voting age herself, that while my issue POSITIONS are consistent, the PRIORITIES are shifting. Gender discrimination and choice are becoming more central, more PERSONAL, to me. So maybe that explains the study.