In reverse - My mother still insists on ring my ex's mother and gran for lengthy chats .even tho we hate each other and she never bothered when we were together!! Drives me mad!
On the other side of the coin I have an ex whose Mother and sister I got on extremely well with. They live in another part of the country but I've always kept in touch with his mother and visit when I'm in the area but NEVER when ex or his current girlfriend are there, I realise his gf might not like it but his Mum was such a sweet lady and very good to me that I couldn't just cut her dead and she didn't want me too so I've just been as sensitive as I could.
my ex's mum is my practise nurse which is awkward if I have to go for an appointment (i was scheduled for a smear test with her but thankfully managed to get another nurse!) but she's always very nice to me and chats away like she did when I was dating her son. I keep bumping into another ex when I'm out with my folks and I'm mortified at the evil looks they give him so I'm glad I'm not getting teh same treatment!