Not sure where to post this and name change cos I think I can be worked out. Will try to be brief but give background...
DSS 15 has a girlfriend (almost certain she's also 15). They went to secondary together for a few years then she moved few hours away so they dont see each other face to face very often at all. We've never met her properly, but somewhat dysfunctional teen when she was around - self harm, getting into fights, threatens suicide, drinks, vapes, has questionable parents - mother is apparently a drinker and I think they have physical fights. From what I gather most of this is still the case. Father still lives near us. She and DSS didn't speak for ages then somehow got back in touch and now have this "long distance" thing...
DH does periodic sweeps of the teens phones as we've had issues in the past of really offensive (not sexual) things being shared on social media etc, and really unpleasant group chats. DSS does know this.
Anyhoo. Recent sweep. Aside from conversation that would make your eyes bleed to death (I'm no prude, but even i need Jesus after this), and making plans to shag in public toilets, she's sent photos. Naked photos and an extremely intimate video (it hasn't been watched but content obvious from the outside).
Not sure what has been sent outgoing from ours, but I'm pretty sure stuff has been shared, almost certainly video called.
So... wtf to do? Obviously it's illegal. Do we do nothing? Make DSS delete content? The mobile phone contract is in DHs name - we don't want explicit content of a fucking minor on a phone number he owns! Might sordid images of an underage girl be backing up on our home PCs if he's saved stuff on google? Ffs...
I'm conscious of the vulnerability of this girl. I'm disgusted at the frankly sordid things the pair of them have been saying. Horrified by the thought of them shagging in the apparently "nice" toilet of a public local venue. Or in a park bush... Terrified she'll get pregnant. Or he'll be stuck with a high drama, suicide-threatening girlfriend if they break up. Between the filth, I think he's a bit smitten, but this smutty child is not the boy we know and love! Apparently she's "experienced" and loves cock. Yay 
We've had so many conversations about not sending/receiving/asking for pictures; respect for females; respect for yourself. It's clearly gone in one ear and straight out the other. I'm honestly shocked at some of the content. I partook in some unwise texting back in the day, but there wasn't talk of sex toys and explicit wank footage when i was 15 ffs. I could cry.
Am I completely out of touch? This isn't normal, is it? Help 