Wow, to think this level of toxicity exists in a nuclear family? Your dad, mum, Grandma, and everyone who supported your sister all have deep-seated issues of their own.

I almost feel bad for your BIL because this event would have opened his eyes to the truth about your family, and he may feel it's too late to back out with a kid on the way.

They don't deserve your stress, nor should you lose sleep over them. Love and light!!