WHOA that interesting I hear that before even Ancient King of England and France used do this long time ago
The difference, as I see it, is that this is not something being hidden behind closed doors. The old saying goes that hypocrisy is the tribute vice plays to virtue, and the pattern among Western rulers who had mistresses on the side was commonly to have a public wife whose children — and those only — would be the legitimate heirs to the throne. What Kim Jong Un is accused of doing is taking another man's wife publicly as his own wife and disrespecting the demand of his recently-deceased father not to do so.
There are many things we do not yet know. However, if it's true that Kim Jong Un is openly being seen with a woman who was only very recently seen publicly pregnant and married to another man, especially if it's true that he was ordered by his father to break off a relationship with her, I can't see how that won't cause problems within North Korea's inner circle.
Even absolute monarchs have to rely on key advisers and family members to retain power. The young North Korean ruler holds his office solely because of the role of his father and grandfather, he doesn't yet have his own base of support. While I'm sure some of the public executions of senior generals were intended to get rid of his enemies and intimidate others, getting away with gross immorality contrary to cultural norms and contrary to his father's explicit orders is not going to be easy.
I can think of two biblical parallels: King David's adultery with Bathsheba, the wife of one of his key military leaders, and then King David's own son Absalom, who, during a revolt against his father, slept with the king's concubines in public to deliberately dishonor his father. Despite his repentance recorded in Psalm 51, David's initial private wickedness led to very public wickedness by his own son that nearly cost him his throne, and led to the death of his son.
II Samuel 14:21-23: http://www.biblegateway.com/passage/?search=2%20Samuel%2016:21-23&version=KJV