Former NBA star Lamar Odom was a "father figure" to Rob Kardashian and, after he left, Kardashian felt "abandoned".

Sources close to the Kardashian clan claimed that this was the real trigger behind Rob Kardashian's downward spiral.

Denying claims that Kardashian's issues had anything to do with Odom's drug use, the reality star and younger brother of Khloe Kardashian was apparently so distraught by Odom's absence that he spun out of control.

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Kardashian had gone through the same devastation when his father O.J. Simpson lawyer, Robert Kardashian, passed away in 2003. Of all the siblings, Rob is said to have never gotten over his grief.

When his older sister Khloe married Odom, Odom quickly became an older brother and somewhat of a father figure to Rob. When Odom was in the picture, Kardashian was motivated to keep healthy and start his own business. Kardashian was said to have idolized the former Laker player.

On "Keeping Up with the Kardashians", Khloe confessed that Rob had told her that his recent issues were triggered by "dark" things that happened in the home when Kardashian was living with the couple.

Many believed that this was in reference to Odom's drug use. However, insiders confirmed that Odom didn't do drugs at home and rather, Khloe and Rob were referring to the constant arguing and breakdown of the Kardashian-Odom marriage.

Insiders revealed that when Odom got deeper into drugs, had more trysts with other women and completely cut off the Kardashian family, Rob went out of control.

Odom had been a best friend and a father figure to him, and he felt that Odom was the only one who could measure up to his deceased father.

When Odom went silent, Kardashian started eating heavily and going deep into drugs and alcohol, which then resulted in his significant weight gain and current health problems.

TagsRob Kardashian, Lamar Odom, Khloe Kardashian, health problems, drug use, weight gain