How would you feel if your partner's best friend was his ex girlfriend who he was in a relationship with for 9 years around 20 years ago? Just to give a bit more info: They speak on the phone every day (not about anything important, just chatter and gossip) they think nothing of meeting up and going for drinks together, and they have been known to reminisce about their relationship whilst I have been present. Feel free to ask more questions about this situation, I'll answer as honestly as I can.