Question

Yes. They did at first. That's how MC joined in.

is it or was it shown and I just don't remember that???? I feel like I don't recall seeing a scene with just them doing something?

It was shown when MC first moves in with them

Or at least among the first times he's at their place. He tells himself he notices a particular bond among them that he doesn't feel part of

Thanks I'm gonna go look again

They kiss. And I think they've fucked in the past, but not since getting with GW. I think Jon has bottomed for Ido. He mentions how big Ido is previously when all three of them do it. GW gets jealous of their relationship.