Vishnu advised the other gods to churn the milky ocean. They would recover a number of lost treasures, including the elixir of immortality and Lakshmi, the goddess of success and wealth. Both of these items would enable the gods to defeat the demons who had taken taken over the universe.Knowing the gods would be unable to churn the great ocean themselves, Vishnu struck a deal with the demons. He told them they would get a share of the treasures, including the elixir of immortality, if they helped to churn. They agreed.
Vishnu told the other gods to use Mount Madura as a stick to churn the waters and Vasuki, the giant serpent, as a rope. Vishnu told the demons to hold the head of the serpent while it wrapped around the mountain. Then they pulled and the mountain churned. As the gods and demons churned, the mountain began to sink into the soft sand bed of the sea.At the request of the gods, Vishnu incarnated as a turtle. He placed the mountain on his back to act as a foundation stone, thus allowing the churning to continue. Some reports say it was churned for a thousand years before anything came up.
When the elixir of immortality finally rose to the surface, the demons rushed to grab it. But Vishnu assumed the form of Mohini, a beautiful woman who captivated all the demons. By her hand she changed the elixir for alcohol and returned the precious liquid to the gods.The churning also brought Lakshmi forth from the ocean. She came as a beautiful woman standing on a lotus flower. Seeing all the gods before her, she chose the god she felt was most worthy of her. Vishnu and she have been inseparable since.
Yes, Vishnu did have family. She/he had a wife named Lakshmi. The avatars of Vishnu were considered the children of Vishnu. It does not exactly say who were Vishnu's children. Vishnu's avatars had many wives (like 16,00 ), so they had many children who were considered children.