I'm not saying this as a shipper, I don't ship any of the psuedo rivals with the protagonists.
But, they seem like they're supposed to be love-interests. They're defiantly not rivals. They aren't even trainers. They're your friends.
May when you play Brendan seems pretty worried about your safety, but that's more in a maternal-sister way.
Brendan though...His "I just saw a huge green Pokémon flying across the sky!....I wish you were there, *name*" line seems pretty romantic. He's also constantly bugging you and helping you.
Dawn..I don't know about Dawn. I never played as Lucas for more then Gardenia's gym. But she's the same as Lucas except for her personality (she's bubbly and Lucas is more of a joker).
Her "Sigh... To be with that special someone in a wonderful Villa like this... I think it's a nice dream to have." line can be taken as romantic though.
Lucas..Is the same as Dawn. Constantly helping you because you're his buddy and you both are helping Rowan. Calling you his friend and such.
Mars calls you and Dawn/Lucas a "lovey-dovey" couple in the english version.
I can't say anything about Kotone and Hibiki since I've never played that game and you can't find much on their interactions online. But they are childhood friends which is a common romance trope.
Anyway, does anyone else think GF is trying to make them seem like love interests?