He looks identical to his son, as he wears a brown shirt. The only differences between him and Squidward are that his shirt is a lighter shade of brown and he wears a red tie and glasses.
He is mentioned in "Krab Borg" when SpongeBob tells Mr. Krabs that Squidward's father never loved him. Squidward then claims that his father loved him very much.
Jeff Tentacles makes his physical debut appearance in the book Hooray for Dads!, indicating he is alive, contrary to what the past tense used when referring to him in "Krab Borg" may indicate. It is possible that he doesn't love Squidward that much. Mr. Tentacles is shown to have a similar personality to his son.