Wetting Problem!

So, my SS is 8 years old and has been toilet trained since age 2-3. However there has always been the odd occasion over the years where he hasn’t made it to the toilet in time or has wet the bed during the night, these occasions were maybe a couple times a month. Then it started slowing and it would only happen once in a blue moon, until about a year ago. My SS now regularly wets the bed when over to stay and also wets his pants throughout the day. It’s pretty clear that he’s embarrassed about it as my partner and I constantly find clothing shoved under his bed in an attempt to hide his wet pants and trousers. We don’t get along with BM so there’s little communication here, but I know for a fact that he also wets himself there too. My issue with it is that I have tried to talk to my partner about this not being normal behaviour for an 8 year old (turning 9 this year), and that we should maybe speak to a Doctor, but he’s just so reluctant to do anything about it aside from constantly reiterating to SS that he needs to talk to us if this happens. Other than this, partner just brushes it off, and I don’t hear a lot being done from BMs side of things either. I’m caught between a rock and a hard place here, as I can only do so much as the step-parent, but I’m getting so sick and tired of my partner dismissing this issue as well as getting to my wits end with everything constantly being covered and smelling of urine (since I do all the washing and cleaning in the house). Not sure what I’m after here; a rant.. advise? Anyone else been in the same boat?