I spoke with a client today that I worked with a week ago. We had spent time clutter busting family space in the dinning room and kitchen. Her kids weren't there when she and I worked together. However they felt the effect of the work. Her son ended up doing some clutter busting on his own in his room. Afterwards he told his mom, "I really feel better when my room is like this."
This has happened before with other clients. I remember working with a client who asked me to work with her teenage daughter. Her daughter said she wasn't interested. So her mom and I clutter busted her mom's office. An hour into it I came downstairs with some trash bags full of clutter and I passed by the daughter's room. She was busy diligently clutter busting on her own.
This doesn't mean that when you clutter bust, your family will follow suit. They may or may not. But they will be positively effected by your letting go of the things that are no longer a part of your life. We are intimately connected to the people we are close with. They feel the resonance of our current state of mind. When you take care of yourself in this way, they'll feel the benefit. They may not know it. But that's okay. It's your silent gift to them.