As mythology shows, Zeus was not really a faithful person and he understood it as a Divine Providence to reproduce with as much women as possible and to have as much children as possible. Probably this explains that his wife Hera got angry and decided to give birth to Hephaestus without any male participation.
But somehow she didn’t like the result and kicked the small Hephaestus immediately after his birth down from the Olympus. The Nymph Thetis found him and took him home. Quite soon she understood that he was not a normal child and saw that he had an unusual ability for craft. Hephaestus loved the fire and knead hot iron with bare hands (for the Romans he was Vulcan).
As it is easy to imagine, Hephaestus never forgave his mother for what she had done to him. As a revenge he fixed her a marvelous throne and sent it to the Olympus. What Hera didn’t know was that if she sat in the chair it would be impossible to stand up again. So it happened and she called for Hephaestus in despair. After a long treatment of Dionysus with a lot of wine, he could elicit the secret from Hephaestus and set Hera free. From this moment Hephaestus was allowed to stay on the top of the Olympus and even got the beautiful Aphrodite as his wife.
However, Aphrodite deceived him several times, mostly with the god of war Ares. One day the god of the sun Helios enlightened the affair and Hephaestus convicted them in the act with a thin net out of gold.
But again he got kicked down from the Olympus for a second time, this time from Zeus. After the strongest fight between Zeus and Hera, Zeus hung her up and tied some stones to her feet. As Hephaestus saw this he set Hera free of pain and got punished by Zeus.
If you want to read more about Hephaestus read “Hephaestus and Zeus“.