I have 2 girls and my 2 yo son all potty training together. They will all usually go in together but one of the girls (3yo) kicks him out as she likes privacy. Which is great I think. She discovered on her own time when she wants to be alone and thats fine!
My son sometimes will pee standing up "like daddy". He pulls a step stool to the toilet but leaves the seat down. So far he has pretty good aim. Not alwasy does he do this though. And he has also mastered pooping on the potty with no problems so I let him pee standing if/when he wants.