Sanaka, Sanandhana, Sanaathana and Sanathkumaara are called collectively Sanakadis in general. They were the mind-born children (sons) of the Creator Brahma. Bhavishyad Puraanam mentions that the Sanakadis were the incarnations of portions of Mahavishnu. Once Brahma praised these Sanakadis the incarnations of Mahavishnu.