In LFB we have the sentence “Is vir est servus et eius domicilium est in silvis Galliae”. The key translate this as “That man is a slave and his dwelling place is in the forests of Gaul”. Given that “Is vir” is the subject of this sentence and also the possessor of the domicilium shouldn’t the reflexive suum be used here instead of eius?
"Is vir est servus et eius domicilium est in silvis Galliae.”
From a syntactical point of view you actually have two separate sentences here, connected by et. The subject of the first is ‘is vir”, the subject of the second is “(eius) domicilium.”
(1) “That man is a slave” and (2) “his dwelling is in the forests of Gaul.”
Compare e.g. “I am a painter and my house is pink”—two different subjects.
You’d have “suum domicilium” only if “is vir” were still the subject of the second. E.g. “is vir suum domicilium in silvis habet”, “that man has his own dwelling in the forests.” (But for “That man has his dwelling in the forests”, without the emphatic “his own”, you’d just have “vir domicilium habet …” with neither eius nor suum.)
Is it not a single sentence with two clauses? Would is always be used instead of suus when the antecedent is the subject of a different clause?
Yes it is a single sentence with two clauses, you’re right, but each clause is grammatically independent of the other. That’s the crucial thing. Instead of the “et” you could have a full stop and the grammar would be the same—two statements each with its own subject. (So you see “sentence” can be a tricky term.)
And it’s not that “is” is used instead of “suus.” They mean different things—“is vir” means “that man” while “suus” means “his/her/its own.” “suum domicilium” would mean “his/her/its own dwelling,” when he/she/it is the subject of the verb (as in e.g. “that man has his own dwelling” is vir suum domicilium habet, or “she kills her own children” suos filios necat).
Hope this helps. It should all become clearer when you get on to reflexive pronouns, e.g. “se” and “sibi,” which likewise refer to the subject (se necat he kills himself vs. eum necat he kills him).
Thanks, I understand now. I was missing that the two clauses are grammatically independent so reflexivity isn’t applicable here.