Hi @Upmama38 and welcome to the online community, we're really glad you reached out for some support.
I can completely understand your concern about this situation - it does seem quite unusual, particularly since your stepchildren are well into their teens. Do you happen to know if this is something that their bio mum has started doing recently, or if it's something that she has always done around the house?
I can hear that you're concerned about this kind of behaviour and how it might be impacting your stepkids, which is absolutely a valid concern. It sounds like a great sign that they feel comfortable telling you about what's been going on with their mum and sharing this kind of information openly. Have they mentioned how they feel about their mother's nudity at home and whether it makes them feel uncomfortable? Do they show any resistance towards staying with their mum?
This seems like quite a concerning situation to learn about, and I can definitely appreciate why you're feeling uneasy about your stepchildren being exposed to this kind of nudity. As you said, it doesn't seem to be incidental nudity like walking from the shower to the bedroom, but rather quite deliberate nudity throughout the house. I'll be sending you an email to check in and discuss your options for addressing this moving forward, so keep an eye on your inbox.
Hang in there @Upmama38. It sounds like you care deeply about your stepkids and that you want them to feel safe and comfortable both when they're in your care and with their mum, too. You have every right to be concerned here 
