You can go stealth NC.
I'm estranged from my mother, father and brother.
And I managed two extended periods of ...
Stealth NC with DH 1.0 's entire family.
Stealth NC lite with DH 2.0's mother.
I'm a NC ninja. 
Stealth NC (lite to start) is where you don't say a damn thing about it.
Slowly slowly you miss more calls. Light and breezy texts for info questions.
Never rising to bait.
Slowly slowly you recycle work/DIY/busy/friend unplannable drama and crisis plus headaches/period pains (to break up the people shaped excuses)... as reasons for not being able to come over, so you end up going over less and less.
Plan meet ups with family members you do want to see in neutral locations. Some cunning timing can help to make sure it's just them. Get them used to meeting you alone, without making a thing out of it. Until it becomes normal.
It gives you a chance to try NC lite on for size. If you decide you want to keep it, it's not such a shock because contact is already decreased for all concerned. And you can "slowly slowly" create full Stealth NC with no big announcement if you take your time with it. If you discover that in smaller doses you can cope and want to keep a foot in the door, then you can stay with reduced time in their company.
Big announcement No Stealth NC can be a bit hardcore, and tricky to manage when the realtionships you want to keep start to revolve around discussions about the relationship you are trying to extract yourself from.
If you aren't sure what you want, which is perfectly normal, Stealth NC super-lite might at least buy you a little breathing space.
oh and...
Becuase nobody wants to be in a position where they even consider this. And I am so deeply sorry you are in a place where losing somebody (that you would much rather keep if they would make some changes) is something you feel you need to think about.