One pro would be 'Support for future generations'. This meaning that Dynasty's can be used to leave a legacy support for multiple generations to come. Any family member (wives, sons, aunts, ect..) in government position have enough knowledge on politics, they know how to care and deal with the people. (So for example, we know if a ruler were to die the kingdom would be passed on to the eldest child)
An Italian diplomat, Niccolò Machiavelli believed that because people were greedy and self-centered, keeping power by any means was the only way to rule.
