It's an ancient tribe, first shown in ORAS. They are vaguely explained and the only members known is Zinnia and her grandmother (Games) and in the manga they have a village, I think they should appear in a next game, due to their unexplained race, in which they should have a better story.
Their Potential Pokemon Team:
I think they should give a hard time to the player, for some difficulty, and they are usually tied to strong Dragon-type Pokemon.
The Salamence and Altaria Family:
They originate from Hoenn, and is one of the signature Pokemon of Zinnia. They can be found in Meteor Falls or outside of it, for the latter, close to their Village.
Pseudo-legendaries Family
Lance, a Dragon Tamer and Elite 4 Member/Champion is a specialist in dragon-type Pokemon, but it is known to use other types of Pokemon from similar designs and power. Zinnia is also known to use other types of Pokemon, Whismur, but not in battle.