うち農家で兄弟も多いからオレが料理することが多かったんだ
Is 農家 normally used for just one person, a family or a place?
If it means "farmhouse" in this sentence, then I think うち could mean "home" and it could be used by the character to make the listener understand that the farmhouse was his home, he invents the word "home-farmhouse"/"farmhouse-home"/"farmhome".
Or is it 内 used as an adverb and it means "internally"? But I've always seen it used as a noun.