I'm an amateur genealogist, and I've traced an (obviously illegitimate) line back to the Arpads that crossed the Carpathians and conquered modern Hungary. I've seen that the Gesta Hungarium decrees that Arpad was descended from Attila, but I cannot find any definite answers. Is this true, fabricated, or simply unknown?
Know this is late and not a proper answer, but since no one else answered oh well. No, they are not. Not even Hungarians claim the Arpad dynasty was desecended from Attila, they claim that they are related, since the Huns and Magyars are considered brothers. At least in Hungarian folklore, that is. It claiming descent most likely means claiming kinship.