There is a genetic aspect to it. My mom found that it increases when they are fighting illness, too. My sister was a bed wetter. My other sister and brother were occasional bed wetters (only when they were coming down with something). Anyhow, what helped in our situation was that when Mom went to bed, she would walk my sleeping sister to the bathroom, pull down her pants and sit her on the toilet. Then she would tell her to pee. She would then my Mom would take her back to her bed. My sister (although her eyes would open and she would talk to my mom) never really woke up. But it kept her from wetting the bed and eventually, she started getting up by herself.
My Mom was also a bed wetter when she was growing up. She said it was really hard because she was a really sound sleeper and would dream that she got out of bed and walked to the bathroom. Me, I wasn't a bed wetter, I was a sleepwalker. The blessing was that I would sleep walk to the bathroom. ;)
Good luck and try to be patient. They have found medically that in some cases the bladder isn't growing as fast as the child and it just takes time for it to catch up. (That is at least what I've heard without the medical jargon.) Hope my Mom's experiences help you out.