My sister and her fiancé have been together for 5 years. We all thought we knew him very well and thought he was a great guy.

That is until last night when my other, single, sister was swiping through tinder and found him on there.

They are due to get married in just a few weeks, what do we do??

We discussed making a fake profile and trying to match with him to see what his intentions are while using it, maybe he just wants to meet friends? Idk. Or should we just tell her straight away?

Please help!

Edit:

His pictures are recent which means he’s actively using it