UPDATE: AITAH sister is mad that I have no reaction to her talking to my ex-girlfriend

I posted yesterday (https://www.reddit.com/r/AITAH/s/NbCHH5R0eO) that for the past couple of months by sister has been talking and regularly meeting up for coffee with my ex-girlfriend. We broke up 20 years ago because she left me for another man and I am now 40, quite happily married and a dad and I had no reaction cos I literally don’t care about the past or what my sister does.

I realised I had never given my sister an exact answer just that I had no visible reaction just that I asked her what she wanted from me and she was frustrated over it.

I ended up calling her not that long ago and we talked about it. I asked why she felt so strongly about wanting to know my feelings about it and a lot of you suspected she wanted approval and you were right. I explained in my original post that my sister and ex were quite good friends and that the friendship ended cos I got cheated on and my sister also felt betrayed. The two hadn’t spoken in 20 years.

When my sister and my ex were friends they did a lot with me and together. They did a lot together and were almost like best friends snd my sister told me that of course she was pissed and felt betrayed about the cheating but also sad because she lost her only genuine friend at that time. I know she has really struggled to maintain good friendships so she said when she happened to bump into my ex by chance and that they picked up where they left from, she leapt at the chance to kickstart their friendship. She said it’s like a fog has been lifted from her and that she feels like she has her best friend back. She said she wanted to tell me but thought I’d be weird about it because at the time, I was so cut up about the breakup. She feels really guilty for being happy about rekindling a friendship with someone who caused me so much pain.

After hearing all that I understand why she wants to maintain the friendship and why she didn’t want to tell me. I explicitly told her that I have no reaction to it because without sounding like a dick I really don’t care who she spends her time with. I told her I feel enough time has passed that I can accept my ex is in her life, especially since my sister told me she is still with the man she left me for and they are married and have a family so they are obviously serious. She also said her daughters (my nieces) are the same age as my ex’s kids and that it would be good for the kids to be friends too which I get as they don’t have many. I like I said have also moved on and have been married for 12 years and I have 3 kids. I basically told my sister if she is looking for my blessing, she has it but that I won’t be involved or really interested in the friendship cos it doesn’t mean anything to me anymore. I also told her she shouldn’t feel guilty as it’s happened, it’s done and I moved on and recovered from it. Like if I saw the ex I would be civil but I wouldn’t be weird or anything about it cos again, I don’t really care. Plus from the sounds of it the ex will really only be mingling with my sister, potentially my BIL and their kids so I may not see her at all.

She left the call feeling at least happier and I’m just glad she has a friend back I suppose. Not an exciting update or anything but I guess a good outcome. We were just mature and civilised.