Bobbi Kristina Brown will not marry rumoured fiancé Nick Gordon anytime soon, according to her aunt.

Whitney Houston and Bobby Brown’s daughter announced her engagement to her “adopted brother” in a recent promo for reality show The Houstons: On Our Own.

Turning to her family, the 19-year-old flashes a sapphire ring and squeals: “We’re engaged!”

But Pat Houston has cast doubt on the wedding plans.

“A lot of teenagers, when they hit 18, they think they’re grown,” she told ABC News, adding, “They think they know it all, they think they know about relationships. You just have to be there to navigate and guide them.”

Pat calls the pair’s engagement “unacceptable” in the TV clip.

And she has suggested her niece will not be planning a wedding in the near future.

“You have to hope that their feelings will not get hurt, but they will,” she said.

Bobbi Kristina and Nick got together following the death of her mother, who had raised Nick but not formally adopted him.

The couple was subject to engagement rumours earlier this year but reportedly called off the plans due to timing issues.