Catalan to English Other History Medieval Catalan

I'm a little puzzled by the use of "sia" in the second part of this sentence:

"com sia vengut e eixit, per la major partida, de Catalunya, ***e li sia al costat***, emperò no es nomena poble català, ans per especial privilegi ha propi nom e es nomena poble valencià"

This is a Medieval quote in a modern text.

So far, my first draft reads: "as they had come or hailed from Catalonia, for the most part, ***???*** but they were not known as Catalans, but rather, by special privilege they had their own name and were called Valencians".

The use of "hailed from" seeks to hint at an archaic language without resorting to "cometh from Catalonia". But to what does ***e li sia al costat*** refer. Perhaps - the area next door? Aragon? Could "sia" be a medieval typo for "seu" here? Don't know how many bishoprics were floating about back then.

This could well be blindingly obvious and I might be off track somewhere. I've been at this since 7:30 ;-)

Thanks in advance for your help / thoughts.