Ethics of being friends with former students?

I’m probably overthinking this but could use a reality check.

I’m a young professor, so often times when I have non-traditional students, they can end up being around the same age as me. I have one student that I taught a year ago who I really enjoyed chatting with during office hours, and recently we ran back into each other on campus and have sort of struck up a friendship.

Important things to clarify: -We are both straight people of the same gender, and both are married, so no romantic overtones whatsoever.

-They are no longer a student of mine, and I can pretty much guarantee I will never teach them again in the future, for various reasons.

-they are not a student in my department, so I will never have them as a TA or have to oversee them in any capacity like that.

They are still, however, a student at a university where I am a professor, so I’m unsure if there is anything strange or questionable about it if we hang out together outside of the school setting. 😅 Any advice? Am I just overthinking this massively?