(Ser) Lantēpsa hen Sȳzvaloti Lentrot.
I suppose 'Sȳrotivaloti' would be technically correct, but 'Sȳzvaloti' sounds better and family names tend not to follow grammar rules as closely as other words. Not sure if there's a way to translate sir/ser, maybe āeksio? Should a title be referred to in vocative (Āeksios Lantēpsus)? The only example I found on the Dothraki wiki is of Daenerys referring to her own title ("I am 'Daenerys Jelmāzmo'"), and that could be both nominative and vocative based on the solar-type -ys ending. So many questions, so little answers.