One Big Family! Leah Messer's Daughters Call Her New Boyfriends' Sons Their 'Brothers'

Leah Messer is getting so serious with her live-in boyfriend, T.R. Dues, their kids are practically siblings!

The Teen Mom 2 star's 6-year-old twins, Ali and Aleeah, call personal trainer Dues' two young sons their "brothers," sources exclusively told RadarOnline.com.

"The girls are very close to T.R.'s boys," a family insider revealed of Tyshawn, 8, and Angelo, 4. "They proudly refer to them as 'brothers' while talking to family members."

The girls also have a new half-sister. Dad Corey Simms, 26, and his wife Miranda Patterson welcomed daughter Remi last month.

"They adore their baby sister," the source insisted. "They are really happy they get so much time with her."

As RadarOnline.com reported, a judge took primary custody of the twins away from Messer, 23, and awarded it to Simms in October, claiming it was in the young girls' best interests.

However, the mother of three is fighting back. She scheduled a hearing in January for the court to reconsider their previous decision.

She's determined to bring her provide a stable home for Ali and Aleeah, which includes longtime boyfriend Dues.

Insiders assure RadarOnline.com that the couple of eight months is going strong, despite reports Messer took back ex-husband #2, Jeremy Calvert.

"Jeremy and Leah are simply co-parenting," a source said of the parents to 2-year-old daughter Addie. "That's it!"