My belief is intuitive, and developed over time, from experience. I'm henotheistic, not strictly polytheistic. I was raised agnostic or soft atheist, a 'none' completely. Being very much an independent thinker, I got to decide for myself, and not borrow other people's thoughts. Siva (my version of the Supreme god) found me first, but later, again from experience, His 'sons' Ganesha, and Murugan introduced themselves to me. They are mystically both emanations of Siva, and both are Gods in their own right, and on the surface, can operate independently of their emanator Siva. They were emanated for specific reasons. If Siva is the sun, both Light and Heat are emanations, both originated by the sun, but out here can be felt and perceived differently.
There is nothing intellectual about it, as it's all in mystical perception and experience. Of course this is just my personal take, and since this is such a diverse planet, I fully expect to read other takes here.