Related for Zevachim 181:28

Everyone is obligated in [saying] Birkat Hamazon (Grace After Meals), Kohanim (Priests), Leviim (Levites), and Yisraelim (Israelites, regular Jews), converts [to Judaism], freed [non-Jewish] slaves, Chalalim (Kohanim who have lost their priestly status), Natinim, Mamzerim (bastards), [a person] castrated by [a deliberate act of another] person, [a person who was] born castrated, [a person] with [one or both] testicles crushed, and [a person] with a cutoff member. All of them are obligated [in saying Birkat Hamazon] and they can absolve others (i.e. say it for others) of their obligation [of saying Birkat Hamazon]. A Tumtum (a person of unknown sex), and a hermaphrodite are obligated [in saying Birkat Hamazon], but they cannot absolve others (i.e. say it for others) of their obligation [of saying Birkat Hamazon].

They mix him the first cup. Beit Shammai says, he blesses on the day and then he blesses on the wine, because the holiday is the direct reason for drinking the wine, and the holiday had already started when the wine was brought to the table. Beit Hillel says, he blesses on the wine and then he blesses on the day, because if we didn't have the wine we wouldn't be saying Kiddush on the holiday at all. Another explanation: the blessing on wine is regularly said and the blessing on the holiday is not. And the halacha is according to Beit Hillel.