I was going to call this killing the relatives, but thought it might be severely misconstrued. The post last week put me in mind of the 'problem' of your hero/heroine's immediate family. Like - do they have one and how much should they feature in the book? Should they feature in the book? And if not, why not?
Some books are built around the idea of family - and close loving relationships, or the hostility that can only be bred amongst people who know each other very well and know about all the buttons to press. And of course home is supposed to be the place where they have to take you in. (Although they might not necessarily welcome you.) These tend not to be romantic suspense, though, or not the way I write it. My protagonists tend to be loners - which throws them nicely onto their own devices or the arms of the other protagonist. Horrible to say and experience in the real world, but bereavement is sometimes a necessity - orphan, widow, sole survivor - or, not quite bereavement - being an only child. I can write from 'what you know' on that one. Relatives and friends of all sorts are a severe handicap when you need to put your protagonists in a position where they have nowhere to turn and no one to help.
Sadly, this means disposing of the family, particularly parents, because whoever else you have in your life and whatever your relationship with them, everybody began life with two of them, even if that is only the biological truth. I was lucky enough to have a close and supportive relationship with mine, and I do know how lucky that makes me. I knew that I could (and did) always turn to them when all else failed. Which is probably why I get one of those pulling-you-out of- the-book moments when I read something when the heroine - and it usually is the heroine - doesn't pick up the phone and call home.
This is why, if you want to isolate your protagonists, the parents (and family) have to go. Hence the high incidence of plane and car crashes that I noted in last week's post, which is where this all began. You can go for various modes of distance, estrangement (which is a story in itself) or physical separation, like sending them somewhere suitably far away - and I have done that. But if you really want to remove them from the scene you have to kill them. Natural causes is an option, but you do have to do it twice for parents, to what are, these days, still relatively young people. Which is how we get back to the car and plane crashes.
I try to be more unusual with my treatment of relatives - so far I have a drive-by shooting, a train wreck and am lining up a house fire. And these are the good guys! I do try not to be too horrible, but it is not easy to be fatal and inventive.
But you should see what I do to the bad guys ...