Do we know if Galad always had the Damodred name, or did he start off as a Mantear? Because with Tigraine being the daughter-heir and presumed next Queen of Andor, I would imagine he should have had his mother's surname, just as Gawyn and Elayne were Trakands.
He would never have been in line for the Lion Throne, but he would have been presumed First Prince of the Sword for whatever sister he wound up having, so again you'd want them having the same surname. Was he taken out of House Mantear when Modrellen died and Trakand became the ruling House? I know Taringail always wanted his son on the Sun Throne, but how would that have worked with him being First Prince of the Sword?
Or do we just assume there was a deal that the first son would be a Damodred, but the rest of the children Mantears?