Ah man, is this normal?

My partner and her father have a strained relationship. Over the past few years he has become very negative and unsupportive of anything she does. Three years ago he was upset that we chose to have a baby and has been overbearing about sharing his opinions on how we raise our kids.

There has been a strain on the relationship ever since, but he has been good to our two older kids so we like them to spend time with him. I found it strange that he sleeps in the same bed with both kids (a boy 10 and a girl 7) but my partner says its not a big deal. At our house they are not allowed to sleep in the same bed, why he doesn't sleep with his wife is beyond me.

WELL... recently we were at a wedding and my wife looked beautiful and dressed very sexy, which she rarely does. Her father was very rude to me, which I shrugged off... but during a father daughter dance he got an erection while dancing with my wife (his adult daughter). She was really disturbed (but made sure not to make a scene or act weird) but she said it brushed up against her and she felt sick.

Is that normal? Does this mean he has some weird sexual hang ups going on in his mind?

Most importantly, now should I worry about my kids spending the night with this man?