The gatekeepers of Parvati’s chambers were Nandi and Bhringi, attendants of Shiva. They never had forbidden him to enter. Shiva often came at inappropriate time.
Parvati’s maids, Jaya and Vijaya, said the gatekeepers have to be subordinate to Parvati, not to Shiva.
Parvati created Ganesha.
The creation of Ganesha is told in numerous variations. This is from the Shiva Purana.