Father Is a Bachelor (1950)

William Holden plays a drifter who comes to a small town and discovers a cabin in the forest where five kids--January, February, March, April, and May--are living on their own. Their parents died a while ago, and they want to keep that a secret from the townspeople, especially the young schoolteacher (Coleen Gray), because they don't want to end up in a children's home and then eventually separated. Holden's character moves in with the kids and poses as their uncle to take care of them while romancing the teacher. However, in order to keep the children, he must get married.