Do you get along with your co-founders really well? Do you feel like you always see eye-to-eye on everything? Then you would probably benefit from adding some “rivals” to your team.
I’ve started reading Team of Rivals a number of times and although something always prevents me from finishing it (the book is excellent, life just always seems to get in the way whenever I pick it up) one of the lessons I’ve drawn from it is that it’s beneficial to surround yourself with people who will challenge you with different perspectives. (This book is really about far more that just that, but cut me some slack here.)
I’ve certainly seen this in practice with founding teams, including some I work very closely with, and have witnessed the benefits of constructive and respectful disagreements that push the team to find the best answers to the problems they are trying to solve for their customers.