Due to the curse of goddess parvathi, gods never give birth to the kids.
According to the story, lord siva and parvathi were in devine dance(romance), one day indra and all other gods known this, they had got fear of thought like 'siva and parvathi' very powerful sakthi, if they given birth to any child, he will be more powerful than us'. So they had devised a plan and was going ask to lord siva as a desire.
Lord siva is kind person, greatest god and father of whole universe. he always come down for their sons(baktas)
So all gods approached to lord siva, when lord siva were in alone. All gods had asked their desire 'dont give birth' in respected manner. Lord siva known every thing, that illeagal desire would went to bad. Lord siva warned the gods, but they did not come down on that desire. Finally maha dev fullfilled their desire.
After some time goddess parvathi known this illegal desire gods got fullfilled by lord siva. Goddess parvathi could not tolarate, got angred, and fire upon gods. Due to which
'She given curse to whole gods would never give birth to their kids'. Thats its gods stopped at 33 million.
अद्य प्रभृति युष्माकमप्रजाः सन्तु पत्नयः || १-३६-२२ एवमुक्त्वा
सुरान्सर्वान् शशाप पृथिवीमपि |
" 'And from now onwards you wives shall remain infertile...' and on
saying this way to all of the gods she also gave a curse to the earth.
Goddess parvathi is also lady(sthri in respect), all woman lifes fullfilled when they given birth.
But she is mother of whole universe, adi para sakthi, she also knows every thing.
----Chaganti koteswara rao garu----