While "the Kardashians adore Scott and tell him he’s part of the family no matter what," the source told Us Weekly that the father-of-three — who shares Mason, 11, Penelope, 9, and Reign, 6 with the KUWTK alum — "feels very distant and feels like an outcast more than ever."
The former flames dated on and off from 2006 to 2015. During the KUWTK reunion special in June, both Disick and Kardashian agreed they would still be together if it had not been for the 38-year-old breaking his sobriety.
Regardless, the two remained extremely close through the years and maintained a friendly co-parenting relationship, with the famed former couple even going on family trips together with their kiddos.
However, Disick and Kardashian's relationship drastically changed once the mother-of-three and Barker's relationship began to heat up earlier this year. (The newly-engaged couple were friends and neighbors for years before taking their relationship to the next level, with them going Instagram Official on Valentine's Day.)
Disick has been having a hard time being around his ex's new man, with the source claiming: "[Scott] avoids family get-togethers that Travis is at, and he has refused to be in the same room with him at times."
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Pointing out the obvious, the source concluded: "It’s fair to say the holidays this year are going to be rough and will be a battle over the kids."
“Yo is this chick ok!????? Brooo like what is this. In the middle of Italy,” the Flip It Like Disick alum allegedly messaged the model about the photo of Kardashian and her now-fiancé making out during their European retreat.
“Outside of coparenting, Scott and Kourtney’s relationship is nonexistent,” an insider said following the explosive August messages.
Shortly after the DM incident, Disick and former girlfriend Amelia Hamlin also called it quits on their near one-year relationship, with a source reportedly saying it was the 20-year-old model "who ended things."
Meanwhile, it seems Kardashian is too busy living on cloud nine with Barker to worry about her baby daddy. The reality star and rocker haven't been shy about flaunting their loved-up romance on social media and during their red carpet appearances.
It's safe to say fans — and Disick — can expect a lot more PDA from the power couple after Barker proposed to Kardashian on Sunday, October 17, at The Rosewood Miramar Beach Hotel in Montecito, Calif., surrounded by rose petals and candles in the shape of a heart.
"[Kourtney] can't wait to marry Travis," dished an insider, who hinted that the 42-year-old has babies on the brain. "She would also love to have a baby with him."