In this sentence:
How can I parse のにも関わらず?
I know にも関わらず means "in spite of" but so does のに and 関わらず. So why use の in にも関わらず?
Also, what is the function of も in this sentence?
Whether it has も makes important difference. (noun)に関わらず means "regardless of (noun)" while (noun/stem of na-adj, verb, i-adj)にも関わらず means "in spite of", as is already mentioned.
As for の, you need it to norminalize a verb when it connects to に関わらず, and it's virtually optional when it comes to にも関わらず. However you can rephrase interrogative clauses like 行くか行かないかに関わらず as 行く行かないに関わらず.