Nobiru Nobi

Nobiru Nobi is Nobita's paternal grandfather, the father-in-law of Tamako Nobi, the husband of Nobita's grandmother, and also the father of Nobirou Nobi and Nobisuke Nobi. When Nobita's father was little, he used to be treated in a disciplined manner by Nobita's grandfather.
Nobita's paternal grandfather passed away before Nobita was born (or Nobisuke had married with Tamako). Nobita's paternal grandfather appears in a few episodes. Nobita and Doraemon meet him by going to the past using a time machine. He appears to love his son a lot, but does not seem to express his affection to his son, so that he doesn't get spoiled.

(Source: Doraemon Wiki)