Well, they're not wrong

I've watched the first episode of Free! but I can never tell the difference between the two (if there even is one ^^')

Are you talking about Free! Iwatobi Swim Club, and Free! Eternal Summer? They're watched in that order :)

I think I watched Eternal Summer on accident.. But it was only the first episode so it's k :3

It's one of my favorites. And I really wish they were gay...especially Rei and Nagisa.

I think I saw fan art of that
Light brown hair and black hair?

That's another ship of mine—Makoto and Haru. Rei has a purplish-blue hair, Nagisa has the blond hair (Nagisa is my favorite).

Ohhh! I think I know who you're talking about