The Collaborative International Dictionary
Grandfatherly \Grand"fa"ther*ly\, a. Like a grandfather in age or manner; kind; benignant; indulgent.
He was a grandfatherly sort of personage.
--Hawthorne.
Douglas Harper's Etymology Dictionary
1824, from grandfather + -ly (1).
Wiktionary
a. 1 In the manner of a grandfather 2 Having the characteristics of a grandfather
Usage examples of "grandfatherly".
The town had a three-block main street, with about a third of the buildings of grandfatherly vintage, made out of adobe brick and sporting Western-style false fronts.
Then in a grandfatherly way, he inquired of his newly-arrived grandsons how they had prospered on their long sojourn away from home.
They kept reelecting him because he was grandfatherly and worked hard to help individuals and families who were having trouble.
The pat was grandfatherly, teacherly, and he looked like everybody's papa.
So, the grandfatherly lecture concluded, we were just going to have to rip out the plants and burn them.