De ritu nuptiarum

Modestinus libro primo regularum.  Nuptiae sunt coniunctio maris et feminae et consortium omnis vitae, divini et humani iuris communicatio. (Marriage is the union of a man and a woman, a partnership for life <the norms of which are > imparted by divine as well as human law).

Paulus libro trigesimo quinto ad edictum.  Nuptiae consistere non possunt nisi consentiant omnes, id est qui coeunt quorumque in potestate sunt. (Marriage cannot take place unless everyone involved consents, that is, those who are being united and those in whose power they are).

Idem libro primo ad Sabinum.  Si nepotem ex filio et neptem ex altero filio in potestate habeam, nuptias inter eos me solo auctore contrahi posse Pomponius scribit et verum est. (According to Pomponius if I have a grandson by one son and a granddaughter by another who are both in my power, my authority alone will be enough to allow them to marry, and this is correct).

Digest 23.2.1-3