How would I know that? If you read info in the NYTimes or Chicago Tribune, it's probably true. If in a celebrity magazine, probably not. Donald Trump has already made it clear that when you are rich, famous and powerful you can have dates and more with beautiful women. Trump Jnr has access to all, and Aubrey Oday is now a celebrity who will move in the same circles.
They are both going to have affairs. Does it matter to anyone outside their close circle who they are dating? Best to concentrate on those you are connected to yourself rather than worry about whether celebrities are having one-night stands, long relationships, cheating relationships or anything else.