You need to build a team for any of your project. None of the sizeable projects can be done by a single person. Building a team is not an easy task, as it involves all kind of right skills in the Project Manager to perform a right kind of permutation and combination to choose perfect match of team members. All team members with same or similar kind of members. Exact sizing need to be done with versatile and variable set of talents so as to build a mix of compliments and supplements kind of people in the team.
Why same kind of team members would not work well. Reason for this could be many but I would like to have opinions from readers.