Bobbi Kristina, the daughter of the late Whitney Houston, is reportedly planning to start a family with her "adopted" brother, Nick Gordon.

According to reports, the 19-year-old is engaged to the boy that Houston unofficially adopted when he was 12 years old. Kristina was reported as keen to have his child despite her family being against the relationship.

A source close to the teenager told Now magazine: "Bobbi's besotted with Nick. She couldn't give a damn what her family think.

"He's her rock - her lover, best friend, her everything. She may still be a teenager, but she's older than her years and she's adamant there's nothing wrong with dating Nick as he isn't a blood relative."

Kristina was spotted recently sporting what appeared to a large engagement ring while showering her beau with very public displays of affection.

Her grandmother Cissy was said to be fuming about the relationship. "What they're doing is incestuous," she said.

IBTimes UK looks at other celebrity unions that did not receive much public support.