Whitney Houston's daughter has fired up in defence of her recent engagement over claims she is set to marry her "brother".

Bobbi Kristina Brown - whose father is singer Bobby Brown - is set to tie the knot with her boyfriend Nick Gordon, who Houston informally adopted when he was 12.

Houston referred to Gordon as her "son" until her death in February, 2012.

The 20-year-old reality TV star, who called off her previous engagement to Gordon in November, 2012, announced the news on her Facebook page, writing: "Yes, me and Nick are engaged. I'm tired of hearing people say, 'Eww you're engaged to your brother' or 'If Whitney was still alive, would we be together or would she approve of this?'

"Let me clear up something, we aren't even real brother and sister, nor is he my adoptive brother. My mum never adopted him. In fact, mummy was the one who even said that she knew that we were going to start dating.

"My mum knows me better than any of you. A lot of y'all are saying that y'all are only saying this all out of love. Which is bull because if that was so, all you would want is for me to be happy."

"People need to seriously stop judging my relationship. Pretty sure it's my own decision who I want to be with. Yes, my relationship may not be perfect. We will have rough patches, just like every other relationship. And we have had our rough patches.

"You may or may not agree with my relationship. You may or may not respect it. Judge me, go ahead. Your opinions are yours and mine are mine. It is my life and not yours. The decisions I make have nothing to do with you. Goodnight."

Bobbi first sparked rumours she was set to marry Gordon after she referred to him as her "gorgeous fiance" in an Instagram picture earlier this month.

- Bang! Showbiz