I was wondering the same thing and was reminded about Jaime using Edmure to negotiate the surrender of Riverrun after Brynden Tully had reclaimed the castle from the Freys in season 6. I just read through Edmure's page on the Game of Thrones wiki to refresh myself on some further details from that encounter.

Walder Frey later mentions that Edmure is back in a cell, although he has no plans to kill him as "killing [his] son by law would not be right." After the celebration, however, Walder is murdered by Edmure's niece Arya Stark.

After killing Lord Walder, Arya uses his face to impersonate him and kill all his sons with poison before riding south. Edmure is presumably still being held captive by the Lannisters.

Good question. I'm a bit foggy on this. If Edmure is alive then is he now the Lord of Riverrun, imprisoned or not?

And are Lannister forces still occupying Riverrun? The Freys's are dead so who is running that place?

@RustyShackleworth said:

Good question. I'm a bit foggy on this. If Edmure is alive then is he now the Lord of Riverrun, imprisoned or not?

And are Lannister forces still occupying Riverrun? The Freys's are dead so who is running that place?

Maybe Jaime will pause on his ride north, let Edmure out, and take him along.