I need insight

Mom here. My daughter is 8 and has never been able to become continent at nighttime. She was difficult to day-time potty train as well when she was younger. She’s had some dry nights, she’s even had multiple nights in a row that she’s dry, but usually is wet. So I feel like it’s possible. I also have custody of my niece since August (we are actually not blood related at all but niece/aunt is the easier way to relate) who will be 17 very soon. She is also a life long bed wetter. Sometimes dry, most of the time she’s not. Neither of them have history of sexual assault (to our knowledge) but my niece has had a fair amount of tragedy in her life (she’s in therapy).

My daughter’s doctor says she will grow out of it, he says this every wellness appointment since she was 5. I’ve cut my niece off of caffeine and soda after 6 to try to rule out causes.

I need to know if anyone out there has experience of long term bedwetting that eventually stopped. I try very hard to keep it all controlled so our home doesn’t have a urine scent but it’s a struggle. We use briefs but the teen pees through them (I get the max absorbent). With my kiddo I took the pull ups away and get her to do affirmations and tell her I believe in her and all that. What else can I do, as a mom, to help them?