AceShowbiz - Whitney Houston realised too late she needed to be a more "present" mother to her daughter Bobbi Kristina Brown, according to her sister-in-law.

The I Will Always Love You hitmaker raised her only child, from her marriage to Bobby Brown, while she juggled her career and battled a substance abuse problem, and although she adored Bobbi Kristina, Whitney wasn't always there for her little girl - something she only recognised in the latter stages of her life.

"She wasn't present (as a mum), as present as she should be," admitted Pat Houston, who also served as the superstar's manager. "She did try at the end, but it was a little bit too late."

Whitney accidentally drowned in a Los Angeles hotel bathtub in February, 2012, with cocaine listed as a contributing factor in her death.

Bobbi Kristina also passed away under eerily similar circumstances in 2015, aged 22.

Earlier this year, singer Bobby Brown cast doubt on the coroner's findings following his ex-wife's death, controversially declaring to Rolling Stone magazine, "I don't think she died from drugs."

"She was really working hard on herself to try to be a sober person and... she was a great woman," he added.

The former New Edition star hasn't explained exactly what he thinks caused Whitney's untimely passing, and it seems his statements have also baffled the tragic icon's relatives.

Asked what she thinks Bobby meant by his remarks, Pat shrugged to breakfast show Today, "You'd have to ask him that, I have no idea."

She declines to offer up her own thoughts on what actually happened on the night of Whitney's death, insisting "only her and God knows that", but she is glad her loved one is no longer suffering.

"I'm at peace (with her death) because I know she's at peace," Pat said, while promoting their eye-opening new documentary Whitney. "She doesn't have to deal with all this anymore, and she was given to us for one moment in time. She served her purpose."