The singer and actress appeared on "The Oprah Winfrey Show" Thursday.
The body of her 7-year-old nephew, Julian King, was found days later in a sport utility vehicle about 10 miles away. All three had been shot.
Hudson shared the pain of her loss with Oprah.
"My grandmother and my mother, even my brother, I can hear him saying to me, 'Jenny, knock it off.' Like right now, my mama be fussing at me. 'Why you always crying? Stop crying. I can't stand when you get out there and singing you start crying,'" Hudson said. "The only thing I can do to honor their memory is to make them proud, and that's what keeps me going."
Oprah asked whether Hudson felt she had healed yet from the murders of her family members.
"I don't almost even know if it has started yet because it's such a shocking thing, and it's a lot to take in that it's like, 'OK, is this real? Did this really happen?'" Hudson said. "It's hard to put it in sync with reality."
Oprah asked Hudson if she parents her son they way her mother cared for her.
"I don't think I could ever come close to be the kind of mother that my mother was to me, but I try to use that as an example and be there for him the way she's been there for me," Hudson said.
Hudson also talked about how she lost 80 pounds. She said her fiance has had trouble adjusting to the attention other men are paying to her since she dropped from a size 16 to a size 6.
Hudson has been a spokeswoman for Weight Watchers.
Last month, the first Disney cruise line ship to debut in more than a decade was christened in Florida with a little help from Hudson. She also appeared at a fundraiser for Chicago mayoral candidate Rahm Emanuel at the House of Blues in Chicago.
The Associated Press contributed to this report.