Have always got in with ex flatmates although particularly close to one (A). The second (B) was very independent and her her own life/would take up invitations but never really reciprocate eg by inviting us to meet her other friends - fine.
Have not lived with them for a year or so now, we all moved out at same time. I have since invited them to an event which we all really enjoyed and have seen each other as a three once after. But B never invites me anywhere and we’re not really in contact, I am with A though.
A initially shared my feelings about B but have just found out that they meet as a two to take part in a shared hobby - incidentally one which I am also interested in. Feel quite hurt and oddly left out, as I feel like I tried to do things as a three (not saying that this should always be the way and it’s onviiuaky fine that they meet on their own!) but neither of them have pushed this. Also feel hurt as I invited B to a group event and she didn’t even repky, then did when I asked again politely to see if she could come - gah