One of my ex-GFs & I had an inside joke. A few months ago, I had a funny-ass encounter with the subject of the joke. So I texted her and told her about it. We had a couple of LOLs about it.

Another one got a big promotion a while back & mentioned it on Facebook. I texted her a congrats & to ask about the new position.

One of them likes still lives up north & likes to send pics of the heavy snowfalls they get. In return, I may send her a pic of me on the beach in January.

Random stuff like that. It's not regular or consistent conversation. But then it's also not strange to send or get a message about something specific.