Have they just completed day-time potty training, and/or are now transitioning to night-time dryness? My daughter is a little younger then he is, and she is now waking up at night to go potty. Or she wakes up and says she has to go potty, even when she doesn't, as she has figured out that it is an acceptable excuse for getting out of bed. We do get up with her to help her use the bathroom, but put her back in her own bed once she is done. We also have a bright night light on a timer, and our rule is when the light is on, she is supposed to be in bed (otherwise she wakes us up too early). That has also helped with getting her compliance in the "it's time to go to bed" ritual -- you just can't argue with a light on a timer :-> . Another thing that I just used with success was a sticker reward system (I actually used a small "candyland" type game and token), and if she didn't get out of bed while the light was on, except to go potty, she could move the token a space the next morning, and when she got to the end, she was rewarded with a special treat (in her case it was a Chuck-E-Cheese outing).
Best Wishes,
A.