Saiki Kumagoro

Saiki Kumagorou is the husband of Saiki Kumiko, Kurumi's mother, the father-in-law of Saiki Kuniharu and grand father of Saiki Kusuo and Saiki Kusuke.

Background
Kumagorou is a grumpy old man who hates Kusuo's father and loves his daughter. He is actually a tsundere who truly wants to dote on her grandchildren.