I know Meg Ryan is the face I remember being in the movie when I saw it. But I looked at her filmography and there doesn’t seem to be the movie I’m looking for there.
A family in a farmhouse one night discovered a lone boy on the swing in their front yard. They invited the kid in and decided to call authorities tomorrow considering the late hour. They fed him, cleaned him up, clothed him with their sons clothes and they all went to bed. Then when they were all asleep, that kid got up and opened the door to let a man who looks to be his accomplice. The man killed the whole family with his shotgun, but spared and took the baby girl they have from her crib. And that girl grew to be Meg Ryan. The man, from what I remember, is Ed Harris. But I’m not so sure now.
Flesh and Bone (1993)?
Has Meg Ryan, and that same plot you described.