Answer:
Adoption, is the right answer.
Explanation:
The term Adoption is used to describe a process through which an individual takes the parenting of a child, from that the legal or biological parents of the child. Along with the filiation, the adoption of the child permanently assigns all rights, obligations a filiation from the biological parent to the person who is adopting the child.
In the given question, since the uncle and aunt who cannot produce a child takes the legal custody of the child that a teenage couple have, this process will be known as the process of adoption
