While it was obviously a difficult time for Khloe, the fact that she had apparently been cheated on probably made moving on a little easier. Plus, it didn't take her too long to rebound with new boyfriend French Montana, so we doubt she's crying herself to sleep every night.
Unfortunately, though, Khloe's brother Rob Kardashian was REALLY close with Lamar and when Lamar got cut out of the family, it was really hard on him.
According to TMZ, Lamar had become sort of a father figure to Rob (the family lost their father back in 2003 and Rob took it the hardest). When Khloe and Lamar called it quits, Rob felt abandoned by that father figure, whom he'd grown to idolize.
The site claims THAT is the reason for Rob's downward spiral, not that Lamar got Rob into drugs, which had become the popular assumption.
We actually feel really bad for Rob. Knowing how he felt about Lamar, we can see how the breakup felt like another loss in his life - and to add insult to injury, the guy he idolized and trusted broke his sister's heart.