Not only that, but apparently they're also wearing the ring, allowing them to receive the actual Etheralus buff LOL. Unfortunately, it doesn't actually do anything or help my healing. The pet also doesn't grow larger, unlike the user(s) of the ring. I guess it's just their small way of cheering me on? I'd like to think so :P
Today I tested it out with a couple other pets just to make sure it wasn't a fluke or anything. It works with all of my battle pets, both ground and flying and some better than others. Green glows for everyone! XD
It was also confirmed on Twitter by @AudrenaWow that the legendary DPS ring also causes a similar effect on pets. It's probably also safe to assume that the legendary tanking ring also gives any pet that you have out an aura.
I hope that this isn't a bug; I find it amusing and fun. It's not really hurting anyone or providing any kind of game breaking buffs/power so what's the harm, right?
Well, I guess it might get annoying for my guildmates since I'm going to pester them to have their pets out during raid even more now. (You thought my getting a Magic Pet Mirror was bad? *cackles* ;3)
But seriously, what a fun find! :D