Is monogamy a human innate behaviour?
Humans are believed to be mostly serial monogamists with a noticeable components of secret cheating. Serial monogamy means most will have a single partner at a time but  will likely have several partners throughout their life, there is however an under current (~15%) of hidden cheating in most studied populations. Also I say mostly becasue human behavior is plastic and nearly every possible combination exists, albeit in small numbers.  Males do have a stronger tendency to seek multiple partners at the same time, which makes biological sense.
 like many social species you really have several mating strategies coexisting, often in the same head. Our large brains allow for more flexible approach to strategies. 

In other animals exclusive (one mate forever) monogamy is exceptionally, almost breathtakingly rare, (not counting animals that only ever mate once). The Azara's night monkey is one of the few that has been backed by genetic research. Almost every monogamous species ever studied either has some rate of cheating, or is serial monogamous.