Dear Curious
That is not unusual at all.
Empty your bladder first, then you are unlikely to pee. However you may gush or squirt, so sitting on a towel is a good idea.
Hope this helps
Dear Curious
Masturbating in private is probably more relaxing and likely to be more satisfying if you don't want others to know what you are doing.
"should I do this when my family leaves?" Unless you want an audience. But what does your family think of masturbation?
"I have to stop from moaning because I share a room with my sister." If you are moaning you may have been close to orgasming, or you may have actually orgasmed. Stopping yourself moaning might make ot more difficult to orgasm. How old is your sister? Is she older or younger than you?
Hope this helps (did I understand your questions correctly?)