A little backstory to this clip before you watch it:

Will Smith’s father abandoned him and his mother when he was a child, and when Will was finally getting into show business and making a name for himself, he tried to sneak his way back into his life like nothing happened. Will co-wrote this episode, and James Avery (Uncle Phil) said “this scene was the hardest thing I’ve ever had to shoot in my life. Every emotion, every word.. that was Will”

Will was actually supposed to play it off and then walk away, and there was originally an alternate scene that was supposed to happen, but he actually completely cut out what was supposed to be said, and did all of his own dialogue. The hug at the end of this scene is completely genuine, and this was a stepping stone in Will’s career where he started to take on the “do what feels, sounds, and looks right” approach to his acting.