Jon Gosselin Will "Most Likely" Take Legal Action Against Ex Kate Gosselin Over Custody Issues, Attorney Says

Exclusive: Lawyer Mark Heller tells E! News that his client feels that Kate has violated certain terms of their previously established custody agreement

Jon Gosselin hasn't been shy about expressing his concern for some of Kate Gosselin's decisions lately. But now he's thinking about taking his concerns to court.

Amid reports that the former Jon & Kate Plus 8 star is planning to sue his ex-wife for primary custody of their 9-year-old sextuplets, his attorney, Mark Heller, confirms to E! News that Jon will "most likely" be taking legal action against Kate over what he perceives to be a violation of a provision of their custody agreement.

This latest disturbance in the Gosselin ranks was seemingly stirred up following a recent round of back and forth in the media, culminating in an awkward appearance by Kate and their 13-year-old twins, Mady and Cara, on the Today show, Jon's negative response and then the twins staying mum about their dad on The View.

Heller explained to E! that a provision in Jon and Kate's arrangement states that, when Kate goes out of town or needs to leave the kids with a babysitter or nanny, Jon has first right of refusal on whomever she picks to do the care-taking, and he can opt to have the children stay with him instead.

Kate has never given Jon that privilege, Heller says, "and from his point of view that has violated the custodial agreement. She always places them with the babysitter instead of the father, to his disdain."

And, Heller continues, Jon has also found that he hasn't been able to spend as much time with the twins as is provided him in the custody agreement due to Kate's "reluctance to abide by that provision for over 12 months."

"In addition, [Jon] hasn't had privileges with his son Collin [one of the sextuplets] since August," Heller adds. "It is his belief that [Kate] has violated the custodial agreement and is actually in contempt of the court order...She has clearly breached those very extensive provisions to the extent he has been deprived very serious parental rights. It is his position that such conduct, and I agree, is not only contemptuous but there have also been attempts by her to alienate him the affections of his children."

Heller says Jon has been consulting with him and it's "most likely that he is going to proceed" in court.

Jon is quoted in the latest issue of In Touch Weekly, meanwhile, saying that every time he sees his kids, "they tell me they want to live with me."