All the grandchildren wanted others, and Grandpa ate three of them

If this is a real riddle or a joke, it is probably aimed at a pun or an unexpected connection of meaning.
The interpretation possibilities can be expanded if we have more context or the original sentence.
If you want to give me more information or the entire sentence in the original, I will be happy to help you with a more correct interpretation or translation.
Good advice:
Riddles like “food and time” are often based on puns, so it is important to correctly understand the context and meaning of the words used.
Such stories or riddles often serve to entertain or teach how “language play” can be fun.