A more thorough explanation:

Fatherly power, also known as patria potestas, is a term used in Roman law to describe the authority held by the male head of a family over his legitimate and adopted children, as well as further descendants in the male line, unless emancipated.

Initially, the father had extensive powers over the family, including the power of life and death. However, over time, the broad nature of the patria potestas gradually became more in the nature of a responsibility to support and maintain family members.

For example, a father could inflict any punishment, including severe ones, on his child without violating any law. He could also sell his child as a slave or put him to death, even after that child had risen to the highest honors in the state. However, the right of putting a child to death fell into disuse over time, and the execution of a son by order of his father was regarded as something strange and monstrous.

The reason why the Romans upheld the patria potestas was due to their profound impression of family unity and the conviction that every family was, and of right ought to be, one body, with one will and one executive.