“Teen Mom 2” stars Leah Messer-Calvert and Corey Simms appear cordial onscreen but behind-the-scenes, the former married couple’s co-parenting situation is not so amicable. InTouch Weekly is alleging that Simms has threatened to fight Messer-Calvert for full custody of their 4-year-old twin daughters Ali and Aleeah, a battle yet to be featured on Season 5B of the MTV reality series.

“A few months ago, Leah asked Corey for more money and it really pissed him off," an insider told the tabloid. "To get back at her he asked for full custody of Ali and Aleeah."

Simms, 25, is rumored to be using Messer-Calvert’s anxiety medication-use, a storyline featured in the current season of “Teen Mom 2,” in order to secure custody. “She couldn’t believe that Corey would stoop so low,” said a source of Messer-Calvert who was reportedly blindsided by her ex’s decision to use her prescription drug use against her in court. “He knows that she’s a good mom,” added the insider.

While Messer-Calvert, 22, has yet to address the custody battle rumors, she did hint at potential behind-the-scenes drama on Twitter last month. “The BEST divorce and custody lawyer! @DivorceLawyerWV,” Messer-Calvert tweeted Aug. 7. “It shouldn’t take being legally appointment to benefit your children’s needs. All I can say is I would be ashamed as a parent/grandparent,” she said Aug. 11.

Messer-Calvert and Simms divorced in 2011 after just six months of marriage. The couple’s story was first featured on the second season of MTV’s docuseries “16 and Pregnant.” Simms married Miranda Patterson in June 2013. In 2012, Messer-Calvert married pipeliner Jeremy Calvert, now 25. The couple welcomed their first child together, Adalynn Faith, in March 2013.

Catch up with the cast of “Teen Mom 2” Wednesdays at 10 p.m. EDT on MTV.