Scott Disick feels "really sad" about Kourtney Kardashian's engagement.
The 38-year-old star knew that Kourtney and Travis Barker were likely to get engaged at some point - but he still feels "low" after they announced the news over the weekend.
A source added: "He will always care for Kourtney. She is the mother of his children and no one else will compare to that."
Scott has Mason, 11, Penelope, nine, and Reign, six, with Kourtney, but the brunette beauty recently got engaged to the music star at the Rosewood Miramar in Montecito, California.
And Scott is apparently avoiding the newly-engaged couple for the time being, as he comes to terms with the situation.
Another insider told E! News: "He will always be a part of the Kardashian family but it is hard for him to be around Kourtney and Travis."
Meanwhile, Megan Fox recently hailed Kourtney and Travis as a "perfect match".
The 35-year-old actress is a good friend of the reality star, and she thinks Kourtney and the Blink-182 rocker are "soulmates".
Megan explained: "I think they're just a perfect match for each other because they have a karmic bond with each other.
"They are soulmates. They love each other and they have a really intense connection."
Travis - who has Landon, 18, and Alabama, 15, with Shanna Moakler - popped the question as the sun was setting at the Rosewood Miramar Beach hotel, and an insider revealed that it was a "very romantic" occasion.
The eyewitness said: "Travis escorted Kourtney down to the beach, where he had red and white florals set up in the shape of a heart. It looked very romantic.
"I could see Kourtney smiling from ear to ear and put her hand over her mouth looking surprised."