Flame point with a brown tabby brother?

So my cat came from a litter that was surrendered to the shelter, so not sure of her parents. There were four flame points (three female and one male) and one brown tabby (male). When they were still at the cat cafe where I worked, the owner didn’t think the brown tabby was part of the same litter, but I did. They were all built very similarly, same age, clearly bonded, and now I know they were dropped off together. But reading about how color works in cats makes me wonder.