Life is a combination of magic and pasta.

It is so hard being the sibling/child that is far away. You are stuck because they are behaving abominably, but if you call your sister out, she will play the "I'm the only one here, and it all falls on my shoulders" card. (Not true, but there are things that obviously work easier for the person who is local)

My mom had to bite her tongue so much about how her younger sister treated their mom - because she kept reminding herself "I'm not there" - but that was in the days before the internet and you have more options to make things happen from far away.

Also, it sounds like your dad is still able to make his wishes known and won't let them steamroll him - my grandmother was always "I don't want to be a burden" and never complained about anything.