Welcome to FT, bren-e!

If the QF scheme is the best one for you (which depends on your travelling habits) and you are going to earn some points in it every year, you can't lose very much by joining as opposed to not joining. The points will stay alive as long as there's some activity in your account once every three years, and you can just add to them as and when. It's better than a smack in the face with a wet fish.

However, you can only collect flying points for your own flying. The family member would have to join separately and earn their own points in their own account. There's a new thing of family transfers now, if you can persuade them to do that for you subsequently, but they would have to join up themselves first.