Identify what is secret and who knows it
A premise may conceal a child's existence, parentage, or connection to an earlier relationship. These are different situations, so read the synopsis carefully. Consider the reason for the secrecy and whose choices could change if the truth emerged; the child should not be assumed to have the same role in every story.
Does this trope always involve a reunion?
No. A reunion is one possible direction, but the conflict may instead concern protection, family recognition, or independence. Second Chance helps locate premises involving renewed relationships, while Single Parent emphasizes the practical and emotional situation of raising a child.