@BertrandRussell
Go to a website that rhymes with "yawnrub".
Look at the Amateur section, especially the Verified Amateur section.
Click on a variety of videos that take your interest, and then click on the uploader's name to see their profile and a list of everything they have uploaded, and also a blurb about who they are.
If the people in the videos are always different people, or there is no blurb, this is not a couple. This is a random guy re-uploading various clips from elsewhere on the internet, or someone doing revenge-porn. I wouldn't watch their content.
If the people in the video are always the same, it is more likely they are a real couple. It is even more likely they are a real couple if they have been posting for a long time (years), they respond publicly to messages, and if both partners have accounts. Obviously this isn't foolproof, but then nothing on the internet ever is. Many couples also upload teaser videos to generate interest, or even non-sexual videos where they discuss various toys or whatever. You can also generally tell whether the sex in the videos is by people who are affectionate together, or if one partner is unaware they are being filmed (bad sign), or seems not to be as into it as the other (bad sign).
I really can't be more specific than that, because the mods probably won't like it.
@DayAfterTomorrow
And how would you feel if a woman brought these up? And would you be honest? Not asking to be confrontational - genuinely curious.
I'd be really happy that they were open to talking about sex in an open and forthright way. I would of course be honest, because an incompatible sex life is an incompatible relationship. As previously mentioned, if they said "I hate all porn and I think all men who watch porn are bad in bed/filth/addicted/misogynists" then that would basically be the end of that. Sorry, but it isn't going to work.