Well I know this has been repeated again and again but some sticking points:
1. Did the father marry a second time BEFORE taking the oath? If so, then there is a very real possibility of his citizenship being revoked. (We have to sign documents saying that we have not committed a crime or have been in trouble with the law before and if it is found that we lied, then citizenship can be revoked).
2. In the eyes of canadian law, the second marriage is not legal - i.e. you were never married. The child is however a canadian citizen because he is born to a citizen (dad). I have no idea what happens if #1 is true.
3. I would still say - get his papers processed. Citizenship laws are becoming harder and harder as time goes on. The child will have a lot more options in the future if he decides to study / settle in canada.
I cant help but being honest and to the point here here - this entire post is extremely creepy and disturbing. I cannot imagine someone taking the oath of canadian citizenship after presumably living here for a number of years and then proceed to commit a crime and justifying it with religion.
He doesn't want to take his son to Canada and he can't take care of him ... The son will stay with his mother but the mother wants to travel to Canada and start a new life with her son as his father has his first wife and 2 kids .
I am really sorry for you.
If you want to start a life in canada you have to immigrate here on express entry or as a student (basically start from scratch). The child however is a canadian citizen and wont have a problem entering or leaving canada.
If the father does not take care of the child then he will probably owe you child support payments.