Roman adoption

In ancient Rome, adoption of boys was a fairly common procedure, particularly in the upper senatorial class. The need for a male heir and the expense of raising children and the Roman inheritance rules (Lex Falcidia) strictly demanding legitimes were strong incentives to have at least one son, but not too many children. Adoption, the obvious solution, also served to cement ties between families, thus fostering and reinforcing alliances. Adoption of girls, however, was much less common.

In the Imperial period, the system also acted as a mechanism for ensuring a smooth succession, the emperor taking his chosen successor as his adopted son.

As Rome was ruled by a select number of powerful families, every senator's duty was to produce sons to inherit the estate, family name and political tradition. However, a large family was an expensive luxury. Daughters had to be provided with a suitable dowry and sons had to be pushed through the political stages of the cursus honorum.

The higher the political status of a family, the higher was the cost. Roman families therefore typically restricted their families to three children. The six children of Appius Claudius Pulcher (lived 1st century BC) were considered unusual. Sometimes, not having enough children proved to be a wrong choice, as infants could die and the lack of male births was always a risk.

For families with too many sons and the ones with no boys at all, adoption was the only solution. Even the wealthy Lucius Aemilius Paullus Macedonicus did not hesitate in giving his two oldest boys up for adoption, one to the Cornelii Scipiones (Scipio Aemilianus, the conqueror of Carthage during the Third Punic War) the other to one of the Fabii Maximi.

...
Wikipedia