Ideas
Switched back to the infant triplet household and the parents finally looked after the infants. The mother could not find infant one, but eventually the butler found her. All three infants are placed in cribs
Switched control to a different sim family. Infant one is missing and mother takes an infant out out of the crib to feed her.
Switched back to the triplet infant's home. Infant two was being fed by her mother, is no longer being fed but is now under the bed extremely hungry. Infants one and three are lost in the world.
I like to play generations. This bug makes it extremely difficult to play the game. With the infants lost in the world their needs deteriorate. Leaving the lot and returning or switching households results in locating the infants and trying to increase their needs.