Nkan Nbe! Grandma caught having sex with grandson

We understand that some persons may be addicted to some bad habits. We understand still that because of the Nigerian culture and beliefs there are things we hold as a taboo in our land.
Should we say some persons were caused from birth or one is suffering from the sins of the parents?

A grandmother was caught having sexual relations with grandson, this is a great shock to the residents of Nyeri town. As a result of the shock, the residents took the victims to the town pastors for special prayer and deliverance. 

Before they were caught, a neighbor heard some funny noises from the granny and thought the grandson was being raped but on reaching the scene they were shocked. The grandson was quick to defend himself that he was only shaving her.  

The resident said the woman was quiet and loving and did not understand why she was tempted to perform such act. They have been detained in Nyeri police station awaiting interrogation.