Ursa brukade aldrig, som jag kan komma ihåg, någon form av böjning i serierna, och det var inte heller underförstått att hon kunde göra en sådan sak. Men , bära hon några "böjgener", som ses i Sökningen och Rök och skugga , där
she had a third child, Kiyi, with the "commoner" Ikem (who's definitely not a firebender - he was attacked by firebenders and fought with swords). Kiyi was revealed in the third issue of Smoke and Shadow to be a firebender. Obviously Zuko and Azula were benders too, but you could have argued that Ozai was a bender to begin with, so that could have stemed from here.
Som det andra svaret nämner är det givetvis inte alla Avatar-efterkommande beviljade som benders.