Depends. You don't have that type of dynasties where the offspring get the crown just due to being the offspring, but you have a few where power has stayed in the family due to nepotism, the ones already in power have maneuvered their children or other close relatives into positions of power more or less just due to their wish to keep the power in the family, and that power in itself seems to have been the main objective, not what they could do with it for the benefit of their country.

Both type of dynasties - royal and nepotism ones - can go good or bad or something in-between depending on the quality of those relatives, and tend to go bad more often because the main objective usually becomes just holding on to the power sooner or later.

But I don't think you should automatically avoid choosing, let's say Barron, or any other of Trump's children or grandchildren - or something like third cousins for that matter, or the child or other relative of any future president - just because they are related and you don't want a dynasty. Might result in avoiding the person who really would be the best alternative at that time. But keep a close eye on them as it can be easier to judge their true quality when they spend most of their life in the public eye.