What are their surnames and given names. For example, is 董 the surname of 董荼那?
In 《三國演義》 孟獲 (Meng Huo) was described as 蠻王 (king of the Barbarian). The fictional characters in his army were supposed to be barbarians. Their names were supposed to be transliteration from barbarian's language. There's no point of trying to find out their surnames.
The funny thing about transliterated name is -- the meaning of the Chinese characters in it are irrelevant. For example, the name '約翰遜' (Johnson) has nothing to do with 約 (approximately) 翰 (writing brush) or 遜 (inferior).
約翰遜's last name is certainly not 約; 約翰遜 is a last name