Marriages were for forging alliances between families by fusing their DNA with children. The PaterFamilias (literally father of the family) has complete dominion over his children, and his daughters marry whoever he allies with at the moment. Pompey the Great was Julius Caesar's mentor/sponsor/co-triumvir. He was married to Caesar's daughter. He was actually so happy with the marriage, that he was mocked for loving his wife. The Romans thought it was very effeminate for a man to love his wife. When Julia died in childbirth, the alliance between Pompey and Caesar ended. When a child is born, the midwife places the child on the ground before the father. Picking up the child makes him legitimate heir of the father, and a roman citizen. The husband can reject paternity by not picking up the child, who will not become a citizen, and can be sold into slavery once he is old enough to be separated from his mother. Divorce can happen at any time. The PaterFamilias might change political parties, and have his daughters marry all new people. Infidelity is very improper for women, still improper for men, although fucking your slaves seems to be okay, and they were all fucking anyway.