How do I tell my family members that I need time alone to practice piano?

I've had this problem, I always wanted to sing,but my family was always coming in and out,so I had stop every now and again. What I did was i said, I'm really sorry but i really need to practice but I'm not reaching where I want to be, so could i just have half an hour or an hour, to practice on my own, and after that they didn't come in until I was finished. Good Luck !!