What happens next depends.
In our family things often blew up, but as drink was involved it was often brushed off as the drink talking.

Good for you by the way, for sticking up for someone who needed your help.

It's possible they will be the type of family to decide your just hysterical and hypersensitive.
Which in some ways is worse than them taking you seriously.

Or they might say your barred from family stuff. Whilst they work on creating a rift between you and your bf.

Thing is these things rarely get better and often become worse once children are involved.
Like you not wanting to leave your kids with drinkers, and the grandma wanting access to her kids.

Stuff like this is horrible to deal with, and you may want to consider just how much involvement you really want with these people.

Does your bf recognise the problems, or does he kind of let them slide cos there family,?