Olivia
He's the heir of a major house. That is the only reason any parent would match their daughter to him. They see the social position and not the trainwreck attached to it. There are very few people Oberon has any respect for and will listen to, so not only does all diplomatic effort fall on the shoulders of those around him, but he also actively offends people without regard for the consequences. He does not care.
I'm convinced that the family has gotten so used to babysitting him and making excuses for him that shielding him from the consequences of his actions has become normal and they have low expectations for him.