Artists conception of parvati ji and her Lord Shiva, as children.

Artists conception of parvati ji and her Lord Shiva, as children. 
Though we do not have a reference to them as a child couple in the scriptures, to me, this suggests in a very beautiful way, not their age, but the very reverse: their ageles, eternal marriage.
There never was a time that Shivji was without Shakti, never a time when Shakti was without Shiva.
Even if it seemed that they were separated, like the period between Sati and parvati, we must not forget that Shakti always existed in her Divine luminous energy fields all over the Universe.
As for the Question, the world prays to Shivparvati, who do shivji parvati pray to?
in my humble opinion, they pay homage to all of creation, they love all beings, whether it is the Gods Vishnuji lakshmiji, Brahmaji saraswati Ma, surya devta, or any devata! any Gana or bhakt, any yogi or sadhu or sadhak! They pray to the miracle of Life as a whole. Aum Namah Shivaya! Jai Durge Ma!