It just never stops, does it?
What a cutie-pie little guy. Three-year-olds usually have lots of energy, curiosity, a sense of self, a fairly good vocabulary, and they know who is good to them and who is not good to them.
Was he, in the grandparents' opinion, too loud, too hungry, too bored, too energetic, etc., for the grands to want to deal with an energetic darling little 3-year-old? All they needed to do was to get him interested in his toys, or a suitable TV show for him to watch, or a glass of milk, or reading a book to him?
Many of us have seen & raised 3 year olds -- they can be a pain sometimes, but there are many, many good, healthy remedies for that.
And his mom -- can you imagine? Sounds like she was trying to become a good mom. SMH.
Fly high, little guy.