The Supreme Court on Thursday ruled that grandparents can legally adopt their own grandchild, even though the child's biological parent is alive, when the arrangement is in the interest of the child's welfare.

The top court ruled in favor grandparents who filed an appeal to adopt their own grandchildren, and transferred the case to a district court in Ulsan, 415 kilometers southeast of Seoul, for a retrial.

The decision was the first Supreme Court ruling which allowed grandparents to adopt their grandchild even if the child has living parents, given that qualifications are met and the arrangement is in the interest of the child's welfare.

The suit was filed after the grandparents wished to adopt their daughter's son. The baby was born while the daughter was still in high school, and was left with the grandparents for upbringing.

The grandson has lived believing that the grandparents are his biological parents. His actual parents divorced while he was an infant.

The Supreme Court decision came following two lower court rulings against the grandparents.

"The fact that the biological mother is alive cannot be a reason to disapprove the adoption sought by the plaintiffs," the court ruled.

It added the adoption should be approved if it is beneficial to the interest of the case's subject, even if it creates confusion in the order and relationship within the family. (Yonhap)