The public razzmatazz surrounding the royal wedding is not the sort of thing Romans went in for on such occasions, but their approval for marriage was unconditional.
It was military triumphs and generals returning loaded with gold and silver that triggered the great public celebrations. Marriage in the Roman world was, for the most part, a private affair. A legal digest defined it as ‘a joining together of a man and a woman, and a partnership for life in all areas, a sharing in human and divine law’. So whatever family interests may have been in play—and Roman aristocratic marriage often looks like a business deal—marriage ultimately depended on the personal will of the couple involved, affectio maritalis bringing and keeping them together. Naturally, marriages broke down, but the ideal was there.
Further, the family home was a holy place, generating strong emotional feelings. The god Limentinus protected the threshold, Forculus the doors and Cardea the hinges (!). The continued worship of the family gods was of prime importance, centred round each household’s Lārēs (guardians), Penātēs (penus, ‘provisions’), and Genius locī (the male spirit of the family’s tribe, gēns, personified in the head of the family).
In this the household reflected its close ties with the state: for Rome too was a ‘family’, with its state Lares and Penates, and the emperor its Genius loci. But though the state never intervened to ratify marriage, it did define the conditions under which children were deemed legitimate—through citizen marriage alone. Further, in the absence of children, it encouraged adoption to keep lines going—not of babies either, but of adults, usually males. The first emperor Augustus, himself adopted by Julius Caesar, had great trouble lining up a suitable successor. It was finally his adopted son Tiberius who took over.
So while Romans would applaud the forthcoming marriage—what could be more important than the head of state’s line?—they would think it an insult that it conferred no greater legitimacy on its offspring than any other union.