Is Zeus is Aphrodites grandfather

Answer 1

Where Midas is the son of the goddess Cybele, he was adopted by King Gordias.

It is then uncertain who his parents were.

Cybele is identified with Rhea, but her parentage is given as Zeus and Gaea.

By Cybele, Midas would then have Zeus for a grandfather, yes.

Answer 2

Aphrodite is actually the daughter of Ouranos. When Kronos usurped his father, he castrated him and tossed his genitals into the ocean. From the foam formed the goddess of Beauty, and from the drops of blood, the ever vengeful Furies. This would technically make Venus a Titan, but since she didn't appear until after the Olympians ruled, she was taken in as one of them. That would make her Zeus' Aunt (because as a daughter of Ouranos, she would be Kronos' sister).