Katherine gets emotional on Leno

Katherine Heigl's voice cracked as she remembered her late brother on Thursday's 'Tonight Show.'

After talking about daughter Naleigh and becoming a mother herself, Heigl described how, until she became a mom, she never understood how horrible it was for her own mother to lose Heigl's brother 20 years ago in a car wreck.

"This is so awful, I'm sorry," Heigl apologized, choking up as she recounted the story and talked about "the overwhelming need to keep her [Naleigh] safe."