At 17 years old, Nick Gordon moved in with Whitney Houston and her then-14-year-old daughter Bobbi Kristina, after Houston asked him to live with them.

“They were very lonely. They were hurting. I guess I was trustworthy, or the guy to move in,” Gordon tells Dr. Phil in an exclusive interview airing Thursday.

“What was going on that was painful for them at the time?” Dr. Phil asks.

WATCH: Nick Gordon Opens Up About Bobbi Kristina’s Downward Spiral After Her Mother’s Death

“Whitney had just [divorced] Bobby, and Krissy had just lost her father, and they were really hurt,” Gordon says. “It’s something that really affected them, especially Krissy.” He adds that Bobbi Kristina didn’t see her father, who had divorced her mother, very often.

Gordon says life at home for him was challenging, and he didn’t want to move to another state with his mother and stepdad, so he agreed.

“I probably wasn’t the brightest child. I gave my mom a couple of problems. I didn’t agree with my stepdad on some things,” Gordon says.

WATCH: Nick Gordon Discusses Bobbi Kristina Brown's Drug Use

After moving in with Houston, he says he developed a close bond with her and considered her like a mother. He says Whitney was “one of the most caring, honest, sweet, genuine people that I’ve ever met.”

“We had a very close relationship,” Gordon says of Houston. “She told me to call her mom.”

While at first, Gordon’s relationship with Bobbi Kristina, he says, was like a brother/sister bond, that changed. “After Whitney passed, of course, it matured into something else,” he says. “First we felt like we only had each other after [Whitney] had passed away. It just became we were around each other all the time and matured from there.”

On Thursday’s episode, Gordon reveals more about their relationship, and shares his story about the night Whitney died and how he told Bobbi Kristina about her mother’s death. And on Friday, he addresses accusations that he murdered Bobbi Kristina.