Complex sentence: Oya has a sister named Ayao that is received by some of her initiates, its ritual and existence is questionable, and it is hard to trace its origins outside of the Lukumi system.
Split into simpler sentences: Oya has a sister named Ayao who is received by some of her initiates. The ritual and existence of Ayao is questionable, and it is hard to trace hr origins outside of the Lukumi system.