Did they ever make cards of the two brothers? I know they have cards related to them but were they ever their own thing like
{Nicol Bolas}?
{Blind Seer} is Urza, though not in card name. And he has many cards that do carry his name, like {Urza's Rage}, Urza's lands, and even {Urza's hot tub}.
Mishra actually does have his own card, {Mishra, Artificer Prodigy}, as well as multiple other cards that use his name.