Can't be brown Leghorn, they have big floppy red combs while your two have a small red comb and what appears to be a black walnut or rosecomb. Also their legs and feather patterns are not the same as a Brown Leghorn. They look like Game Bird mixes.
It's pretty hard to tell mixed breed parentage unless 2 pure bred parents were used and the result is a common hybrid.
You don't have that here. What you do have are some body characteristics that indicate game is in the mix due to the smaller size and the tails.
Leghorns have a bit of a game looking tail, though fuller, but it is nearly impossible to predict them in part of the parentage. Many game types lay white eggs too. With the lack of very large floppy comb, I too doubt Leghorn in the background, but it is possible.
In a situation where many breeds of birds are running lose, you get hybrids of hybrids and original parentage is completely blurred.
Backyard mixes are a lot of fun and generally hardy and prolific layers. I've enjoyed my backyard mixes.