Jesse James admits it's hard to see Sandra Bullock raising adopted baby boy Louis Bardo, 4 months.
The photos "made me sad," James, 41, tells Nightline in an interview to air Tuesday night.
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"But I realize why things have to be done in a certain way," he continued, referring to adoption agencies possibly looking down on his affair with tattoo model Michelle "Bombshell" McGee. Bullock is adopting the baby boy as a single parent now.
James said he and Bullock, 45, found out the adoption had gone through around Christmas, and Louis joined their family on New Year's Day.
When asked why he adopted a black child, James said he "didn't care what color" the baby was. "My only prerequisite for adopting a baby: I want the baby that needs us the most."
James said that watching Bullock as a mother strengthened their relationship.
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"To see her in the role as mother is, like, one of the most amazing things I've ever seen. She is like a fish to water ... as soon as she put that baby into her hands, it was automatic and amazing," James said of Bullock, who also helped raise his three children from two prior marriages. "I found a new trust for her, like I knew she wasn't going to leave, and our relationship blossomed."
But he "threw away" their "amazing marriage" -- and "wanted to get caught," James said.
James thinks Bullock "had her suspicions" about his prior infidelity.
"But, you know, I lied, and lied my way out of it," he said. "I lied to everyone about everything, even to myself."
VIDEO: Jesse says he threw away his marriage
He said she was "proud" of him when he checked into rehab following news of his affairs.
"I just told her I was going to get some help and I wanted to make sure she would take care of [his daughter] Sunny," James said.
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James explained that he's opening up about the breakdown of his marriage of nearly five years because he was slammed for being racist and anti-Semitic following Us Weekly's exclusive photos of him giving the Heil Hitler salute.
"Dealing with losing my marriage and my son and embarrassing everyone and decimating my life..." he said, "but to be called a racist on top of that is, it makes me really sad."
Of the photos, James said, "I could tell by the look on my face it was a joke that was funny then, probably for a minute, but then looking at it in the context of now and in my life, it's not funny... There's not a racist bone in my body."