Coworkers with a superiority complex are the worst, but being related to them puts their antics into another league altogether. 

While it may be true that a certain amount of competitiveness can be a healthy addition to the workplace, there comes a point where it stops driving anybody to better and starts being a long and drawn-out performance of a person’s unaddressed insecurities. Just because it is important to care about doing your own work to the highest standard doesn’t mean that it is acceptable to ignore that you are a part of a team.