Welcome to our forum.
I posted on your other thread, and noticed many other people have posted as well and gave good advice. So take advantage of that, you'll want to start working on things right away, and not wait for them to get worse.
You do have rights, and you should speak up when you have a want or need. C and D should be doing likewise. Communication tends to be easier when it's done sooner rather than later. And communication is probably the most crucial part of this puzzle.
I hope all three of you will have some emotional relief soon.
Love means never having to say, "Put down that meat cleaver!"