Old flame (30) and I (33) are back in contact… but it’s not so simple - what would you do?

Old flame resurfaced… not sure what to think (would love to hear what you think)

When I was 26 I dated a guy who was 23. He was in my city (let’s call it Narnia) for a master’s program. I knew it probably wouldn’t turn into anything long-term since he was younger, moving around for school, and figuring out his next steps and were in different places, but we genuinely enjoyed each other, had a lot in common, plus heaps of connection and chemistry. We stayed in touch after he left, and I even visited him once. Nothing dramatic ended it, but it faded in a sort of sad and bitter way (as I suspected would happen, bc of the aforementioned).

We both moved on, got new partners, and only saw each other’s lives through occasional glimpses on social media.

Three years later, completely out of nowhere, we ran into each other in a supermarket back in Narnia (where I was still living). He had moved back for work that very weekend, and I was actually leaving Narnia that very same weekend for a new job in a new city. It was such an unexpected encounter - we exchanged a quick hello/update, then moved on.

Since then, I’ve broken up with my ex (and still live in the new town I’d moved away to).

About three weeks ago, I got a totally out of the blue message from him asking me how I am, saying he thinks about me all the time, never forgot me, and always wondered “what if.” (The supermarket meet up was 2 years ago, btw - and now we are 33 and 30).

I don’t live in Narnia anymore, but on the exact day he messaged me, I happened to en route back there for a week long work trip. I debated replying, but eventually did and asked if he wanted to get coffee.

We met up and ended up talking for hours. The connection came back instantly.

Here’s the catch: he’s still with his girlfriend. He says they’re in a dead, loveless relationship, in the throes of breaking up, but it’s messy because they live together and are stuck in a lease. I’ve been in that situation before so I get how slow and complicated the end stage can be.

I told him I’m not going to cheat or entertain anything romantic until he’s fully out of that relationship. He said understands completely.

I know I need to be careful. But the spark is still very real, and we have so much in common.

I’m not even sure what kind of advice I’m looking for. Just wondering if anyone else has been in a situation like this, where someone from your past reappears (and it’s kinda messy?).