OP: I left a 21 year relationship in Feb 2017. In May that year I hooked up with a person I knew through friends. Was a FWB kind of situation, I didn't want anyone knowing because of ex, I didn't want it to be public etc. We spent 6 months together as much as we could, the chemistry and attraction was very strong. But we have very very different lives, I have kids for a start. Anyway, we got quite close both started to get feelings and both of us started to pull away. The timing wasn't right. At the time he told me he had met someone at a party he liked, and he was conflicted what to do. I told him to go forth and conquer and I dwelled on it for a day, missed him a little bit but got on with my life, joined tinder and had a ball for 7 months.
We started to see each other again before the last summer, after 7 months not even really speaking (it all ended very amicably and I wasn't that invested), picked up where we left off, but something had changed in us both. I felt much better emotionally and started to open up more, he realised how much he liked me etc. He actually wanted me to go off see other people etc as he couldn't wrap his head round the fact that I had just left a long term relationship (since the age of 17) and didnt WANT to be single for a while.
Well, i did that, and I still gravitated back to him. Partly because no one matches up with him in terms of chemistry and the bedroom. Since sept we have got very close, we spend a lot of time together. Hes proven himself to be kind, considerate, honest, smart, open, affectionate and just all round lovely. I didn't get much of that first time round, although I knew he was a good person (we have mutual friends that have known him for years).
My point is, I could have told him to fuck off when he got back in contact, but feelings were there on both sides. If you keep an open mind, and communicate well, it is possible to reconnect with someone. I didn't "in love" with him before, I'm learning to fall in love with him now. But thats more about me than him. Sometimes people enter relationships and it opens up all sorts of past wounds and vulnerabilites, so its not always cut and dried.
Not trying to get your hopes up and you'll get loads of replies that look cut and dried, but life is life and its not always in a straight line.