EN
There are two species of Roman adoption: adoptio sensu stricto and adrogatio. Fragilitas adoptionis mentioned by Justinian means that adoption is focused on the political purposes and disregards the rights of the father. The motive of the act of adoption is not childlessness, but the desire to acquire those civil and agnate rights which are founded on the patria potestas. There is also a maxim adoptio naturam imitatur, which requires the adoptive father to be at least eighteen years older than the adopted children.