Question about the abductions *SPOILERS*
It's a fairly simple one, what was the purpose of the child abduction and murders to the elderly couple? The priest states he killed the man because he admitted to murdering 16 children in confession and would kill more. The Aunt had obviously kidnapped at least a further 2 children (Anna and Joy) after her husband's disappearance , but what was the couples continual motive? There didn't seem to be any obvious hint to molestation, just puzzle/snake torture followed by death.
I feel like I may have missed something obvious that fits it all together, but perhaps it's to do with losing their son at an early age and a twisted satisfaction in seeing other parents grief? Any thoughts?