The late singer is said to have taken Nick Gordon, 22, into her home in Atlanta, Georgia, when he was a troubled youngster in an attempt to transform his life.
Houston never formally adopted Gordon, but he called her "mum" and was treated as part of the family, also becoming a brother to her 18-year-old daughter Bobbi Kristina Brown, according to The Sun.
"Nick was family, she loved him as much as any mother could love a child. Whitney wanted to save Nick - even if she couldn't save herself," a family source told the paper.
"If he is not written into her will and everything goes to Bobbi, then it will only be because it was written before she took Nick into her family.
"If that's the case, Bobbi will make sure Nick is taken care of because it's what her mum would have wanted and he's like a brother."
Gordon was charged with gun possession in Roswell, Georgia, back in 2011 after pulling a gun while trying to stop a fight between Bobbi Kristina and her ex-boyfriend.
Bobbi Kristina was arrested for possession of alcohol while a minor on the same night.
More Whitney Houston coverage:
> Whitney Houston funeral takes place in New Jersey
> Whitney Houston funeral footage sold for Bobbi Kristina Brown
> Whitney Houston 1963-2012: Reactions
> Whitney Houston 1963-2012: Obituary
> Whitney Houston: Greatest musical achievements - pictures
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