My wife does upvote my posts, and I upvote hers... that's a slightly less insidious form of nepotism...

If it's "social media", then I would expect that family and friends would get more up-votes than random strangers. That's part of the equation when you're evaluating subjective value from your own perspective.

I don't even have a problem with self-upvoting, provided that it's not coupled with spammy content. IMO, the problem isn't self-voting. The problem is the incentive that self-voting might create for people to intentionally produce and vote on low-value content. That would be sort of like a form of embezzling.

We paid/contributed to earn the right to vote. That includes the right to vote on our own stuff, and our family's.