Friend recently became a second wife. I have questions

Salam guys,

My friend is very happy alhumdullilah with her marriage.

I had random thoughts though. Wonder if anyone has been in a marriage with a man with multiple wives.

1st question - kids: the kids are technically Brothers and sisters even if they have different moms. Do the kids spend time together as siblings in the same place, or no?

2nd question- wives: do the wives ever spend time together? Do they help eachother out with kids? Is this normal?

3rd question- jealousy: does jealousy ever subside? How do wives go about this?

These are genuine questions that popped in my mind. No harm meant by it!