Sanatan Dharma - Vishnu Brahma & Shiva in Sanatan Dharma

Vishnu is the Deva who maintains many bhaav. He operates in many loka according to that loka. His Devi is Vishnuvi and she assists him in the same task of maintaining bhaav. Only their rupa or outer manifestation changes according to loka.

Brahma takes care of understanding. This understanding is of inner nature of all jiva. His Devi is Brahmi and she assists him in this task. They and other deva stay away from knowledge or gyan which relates to the outer world. They too work according to loka.

Shiva is he who always is. His Devi is Shakti. Both of them maintain many loka. Different tasks are required to maintain different loka and Shiva/Shakti are engaged in those tasks.