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The sister of Tad Cummins, the former Tennessee teacher accused of kidnapping a 15-year-old student, says he must face up to his “horrible” actions — but she still loves him.

Daphne Quinn told NBC News in an exclusive interview, to be aired Monday morning on TODAY, that she wants everyone to know her brother is not a monster.

Cummins, 50, is due to appear Monday at a federal courthouse charged with sexual contact and aggravated kidnapping of Elizabeth Thomas after police found the pair more than 2,000 miles away from home in a remote cabin in northern California.

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During their 39 days on the run, the pair was caught on surveillance video at an Oklahoma Walmart and police say they stayed at cheap motels with one bed.

Cummins was Thomas' forensics teacher at their high school in Maury County, south of Nashville. Police say he had been researching teen marriages and was seen kissing Thomas at the school earlier in the year.

Quinn says she spoke to Cummins three times over the weekend.

“He's done this horrible thing, that he has to pay for,” she told NBC News. “But he's still my brother and I love him.”

Meanwhile, Thomas' family lawyer says the teen was "evaluated and treated" by mental health experts before her return home to Columbia, Tennessee.

"There is no doubt that she suffered severe emotional trauma and that her process of recovery is only just beginning," he said Friday.

Speaking to reporters in California Friday, Siskiyou County Sheriff Jon Lopey said Cummins was cooperative in the arrest and that Thomas' emotions indicated they had a "relationship."

"I can tell you that her mood was kind of escalated ... you know sometimes she was emotional, you know it was a very traumatic experience for her," Lopey said. "It was kind of a roller coaster of emotions for her."