One factor not mentioned is sibling spouses.
It can be a most unpleasant experience, for example, if a sibling has married someone who is liberal, or otherwise out of step with other family members.
We all met our siblings in law as adults; there is no shared childhood connection with them.
Point being, in family gatherings, holidays, any family event, these siblings in law, with whom you never had any bonding, are there, and will affect the family dynamic and interaction.
You might have had the finest relationship with your sister, for example, but if she marries an opinionated know it all liberal, you aren’t going to enjoy the family visits.
Yup. I have an ahole of a bil.