Relationships are hard. Singlehood is difficult. "Choose your hard" is the saying. One man preferred pleasure over cheating.
His wife found him a girlfriend to stop him straying. Most guys would name her wife of the year. She found him a doppelganger. Both women are lovely.
Despite being in relationships, most men and women still date. If the situation was right, most would cheat on their spouse. Several "modern" relationships result.
Some have many relationships. If one person wants children but the other doesn't, they may date someone else to have children.
This man seems to be living the life. His wife was attractive. His wife prevented affairs. She found her spouse a girlfriend.
She got her spouse a girlfriend who looks like her. Now he can enjoy his wife and identical girlfriend. The three live and date.