"Brake line fittings"? You mean "Tube nuts"? If so, I'd expect most of 'em to be steel, not brass.
Moreover, I'd expect at least some of them to be different thread size than others, since there's two different sizes of tubing.
I just bought a couple bags of tube nuts for 3/16" and 1/4" tubing from Summit. They come as an assortment of thread sizes for each size of tubing.
3/16
https://www.summitracing.com/parts/sum-220137
1/4
https://www.summitracing.com/parts/sum-220115
Summit also has tube nuts in Stainless, and in larger tubing sizes.