Cronus.
They were both king of the gods. Cronus was king of the gods until Zeus was.
Only such god as Allah
They were in origin the gods of the land, sea, and sky, and they were created to explain the 'why' of the natural world.
The Titans? Like, Kronos (Zeus, Posiedon, and Hades dad)?
Most of them were very wise while gods like Ares and Hades were not the brightest.
Apollo and Zeus - her brother and father.
In Greek Mythology, Zeus didnt hate Hades. Hades didnt like Zeus or Poseidon because they stuck him in the Underworld.
No never, Hades isn't evil and is Zeus's oldest sibling with Zeus being the youngest. Hades also is the most reasonable of the gods and isn't stupid enough to let his anger get the best of him unless it's a lowly human soul and only if they do something really bad like try to rape his wife Persephone. Hades has fought with Zeus vs the Titans but that's about it.
Well, Zeus is usually seen as the leader of the gods, but the big three were Zeus, Poseidon, and Hades. If you're asking if there's one "God" like in Christianity, then no, there isn't. There are lots of gods.
Zeus doesn't dislike Hades, he just finds him morbid and dark.
If you are asking 'did Zeus allow Hades to marry Persephone', then yes, he did.
The Titans were the rulers of the world until Zeus forced Kronos, the ruler of the Titans, to spit up his siblings. Zeus, Poseidon, Hades, Hera, Demeter, and Hestia chopped up their father into millions of pieces and the Titans were over thrown. They are the parents of the gods. They were just like the gods only one generation before, and with a different name.