It's incredibly vague indeed.

Thanks to the time issue I see Mateus as being at last four years (physically) her junior. The TECHNICAL difference is something I've never given much hard thought for (because it turns my head upside down GAAAAAH).

I'm trying my damnedest to make this make sense but my brain's not working. Too much caffeine? Too little sleep? Too few calories? I DUNNO.'

I don't think that he's around Kefka's age (which would be 35). For some reason that doesn't seem to work at all.