Yes.
Pick up each bird and have a look at her vent (butt hole). A layer will have a vent that looks like an egg could come out: it's sort of moist and stretchy-looking, and almost as wide as an egg. A non-layer has a much smaller, puckered looking vent.
Once you've seen both versions, they...
I suggest one of each. It is not obvious which breed is better, so keeping one of each will get you one of the better breed, and one of the other for comparison :)
Edit--oops, just re-read the first post, and the Sussex are inclined to bully the Brahmas. Nope, better to keep two of a kind. In...