Charley Gallay / Getty Images North America 1 / 9
Charley Gallay / Getty Images North America 1 / 9

Heidi Montag is standing by him despite his recent arrest for child sexual abuse.

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Not only is the former "Hills" star supporting him, but she also thinks Bill Montag is entirely innocent.

"It's all coming from an estranged family member with ulterior motives," the source close to the reality-TV star told Us Weekly. "Heidi doesn't believe any of it."

"She grew up in that house and knows her father's character," the source adds, "and 100 percent believes all of the accusations are false."

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Bill was arrested on Jan. 29 in Aspen, Colo., on charges of incest and child sexual abuse. The accusations are graphic and, according to court documents, the abuse stretched from 1993-1997.

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At the time of the arrest, a source close to Heidi told TMZ that the accuser was "determined to destroy the family."