This Is Us star Sterling K Brown left Kelly Clarkson in tears when he revealed the heartfelt reason why he changed his name ...

This Is Us actor Sterling K. Brown chose to go by his middle name Kelby until he was a teenager and shared the heartwarming reason he decided to switch back to Sterling.

And he wasn't the only "This Is Us" actor in attendance ... (Fitch himself played a teenage and young adult version of Randall Pearson throughout the series.) Zeile reshared Fitch's photo to ...