Wasn’t house Yronwood the only dornish house that supported the blackfyres? I thought the santagars stayed with the martells

Well, the Wyls are Yronwood bannermen and like a scrap, so I think they supported the Blackfyres.

The Santagars is my guess based on Spotted Tom being an exiled knight from Westeros, and the Santagars being the Knights of Spottswood. 

And the Yronwoods are the only ones we know of. Absence of evidence not being evidence of absence.