15 V.S.A. § 1203: Person shall not enter a civil union with a relative

(a) A woman shall not enter a civil union with her mother, grandmother, daughter, granddaughter, sister, brother’s daughter, sister’s daughter, father’s sister, or mother’s sister.

(b) A man shall not enter a civil union with his father, grandfather, son, grandson, brother, brother’s son, sister’s son, father’s brother, or mother’s brother.

(c) A civil union between persons prohibited from entering a civil union in subsection (a) or (b) of this section is void.