EXCLUSIVE: Mary Jo Eustace Speaks Out on Dean McDermott's Alleged Missed Child Support Pay

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Dean McDermott's first wife, Mary Jo Eustace, is claiming the actor owes five months' worth of child support payments in a new lawsuit. ET's Cameron Mathison got an exclusive sit-down with Eustace, who gave her side of the story.

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"I can't imagine not paying your child support," Eustace told Mathison, explaining that she can't think of an explanation for why McDermott would miss the court-ordered payments. "It's a legal obligation. I can't imagine not paying that and letting that lapse and that's why I had to get an advocate to see what we can do about that situation. It doesn't make any logical sense to me either - why that would happen. In my mind, that's something you would never want to be made public. You would want to make sure that was taken care of, because that's a pretty bad thing. I don't get the whole picture at all, because it seems that it all could be avoidable."

The petition filed in California Superior Court claims that McDermott owes $8,700 in back child support payments for the former couple's 16-year-old son, Jack. Eustace told ET that she has reached out to McDermott "many times" about the alleged missed payments to try and get a timeline on when she can expect the money, but according to her, she has gotten no responses.

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McDermott's current wife, Tori Spelling, claimed that the family had been living "paycheck-to-paycheck" on an episode of their reality show True Tori last year, and there have been indications of downsizing lately, as the family moved into a smaller home earlier this year. This has led some to wonder if McDermott simply can't afford to make payments, but Eustace argued otherwise.

"They still have a great lifestyle," Eustace said. "I think when you move from a 6,000-square-foot house to a 4,000-square-foot house, that's not a drastic difference in your lifestyle. I don't think objectively there's a way bigger difference ... And then you also consider the Spelling empire. I mean, it doesn't really make a whole lot of sense."

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ET reached out to McDermott for comment with no response.

McDermott and Eustace divorced in 2006 after McDermott cheated on her with Spelling. Later that same year, McDermott and Spelling tied the knot and have four children together -- Liam, 8, Stella, 7, Hattie, 3 and Finn, 2.