A good leader needs to have a strong relationship with everyone on his or her team. The more you know about them and the more connected you are, the more effective you become. So on the one hand, you need to be close with your subordinates…but not too close.
You cross the line when someone on your team expects to be treated differently or held to a different standard than the rest of the team. This creates a division within the team and undermines your credibility as a leader. Your priority should always be the success of the team and you should make sure this is understood and supported by everyone. If someone loses sight of the relationship and sees you as a friend rather than the team lead, explain that your job as a leader is to ensure the team wins. And the way you’re going to ensure the team wins is by setting high standards that are the same for everyone.
Playing favorites or giving special treatment hurts you, the other person, and the team.