|Freedom demands courage|
You may be in a situation where you'd have to be nice to people you really don't like. Being nicer to those who annoy you and they keep annoying you because you have no other choice but to be nice to them out of courtesy. I say it's time you let them know you don't like them. All because you have family terms with them, so you can't actually ask them not to keep poking their noses into your very personal family matters and your life; sounds quite unfair. You are a slave to your own thinking here. Try breaking free and having the courage to ask them not to meddle in your life.
When you gather the courage to ask a stronger annoying person to back off, you become a free man. So go get your freedom!