"He'll be the bad guy again," the source said.
"Nick knew that a lot of the family weren't fans of his; he sort of kept her away from some of her family members because he didn't want [the family] to say bad things about him to [Bobbi Kristina]. It's not exactly his fault."
According to the family member, Nick – who was raised as part of Whitney Houston's family but never formally adopted – didn't get along with members of Houston's family, particularly the late singer's mother, Cissy Houston.
The source continued: "Everyone had a preconceived notion about him, and it wasn't always fair. But he didn't do himself any favors. He was disrespectful a lot of the time, always 'f' this and 'f' that, using language that Cissy didn't approve of. To her face. If there's one thing that Cissy doesn't stand for, it's people who swear in front of her."
Bobbi Kristina, 21, and Nick's unconventional romance has raised eyebrows over the years. The pair went public with their relationship shortly after Houston's death in 2012, and they officially tied the knot last January.
Christopher Polk / WireImage
"I don't want to blame Nick for any drug use, because that's not fair," they said. "Bobby was blamed for Whitney's drug use, and that always bothered him. She was a grown woman who made her own choices."
"Krissy makes her own choices, too," the source continued. "No one influences her to do anything she doesn't want to do; she's stubborn just like both of her parents. Nick may not be the best influence on her, but she makes her own choices."
"She said, 'I know how my mother died, and I've learned from her mistakes,' " the source recalls. "She seemed very adamant."
Reporting by STEVE HELLING
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Courtesy Bobbi Kristina Brown