Xin and Demacia: how old is he?

So in the original lore, Xin was a Noxian prisoner of war turned gladiator that became in-dept to J2 and as such became a Demacian. This meant that even in the old lore, he was of a considerable age because he served under J3 and alongside J4. This is assuming he also spent a few years under J2 and didn’t directly serve under J3.

But in the new lore we learn that J1 was around a long time ago. Long enough for Sion to fade into memory after killing him. So what does this mean for Xin?

If we’re going on the original lore, that would mean from J2 and onward they decided to stick with the name Jarvan when Royalty doesn’t actually have to do this (and imo it’d be awkward since J1 had been dead for at least a century maybe). If that’s the case, Xin was probably brought into service near the end of J2 as we are currently on prince J4.

Unless

They could make it so J3 saved Xin and that would make him more recent and possibly less ancient. Because if it’s J2, I feel that Xin would be pushing 50 with J4’s current age. But with J3 he could be pushing 40.

I think the latter makes more sense as Xin doesn’t look that old. And it helps cement still that Xin is J4’s senior.

So how old is Xin?