@tattedese - it is a 'no brainer' for 2020 because from what you stated, Baby was in the hospital from the date of birth until Dec 31 and beyond. That is "temporary" living away from home and therefore Baby permanently lived at home in 2020 in the eyes of the IRS.
As long as you and Mother did not live at Grandfather's home (you didn't state either way), Grandfather can not state Baby lived with him in 2020.
