Then you are clearly reading a different story than this one, since the ML is the one who stayed, and it was his siblings (and the FL) who were sent away for several years.
And though that might explain Eugene liking Hari, she won Cabel over as family within five chapters, well before they moved out.
They did hint at Eugene having feelings for her, but those feelings weren't romantic at the time, only significant. It took him several years to fall in love with Hari.
However, please note that Hari and Eugene didn't separate in the original timeline and he still fell in love with her (he just had no opportunity to do anything about it, since she asked him to find her a husband while he was in the middle of getting divorced), so all their splitting up in this timeline really did was speed up his revelation. ╮( ̄▽ ̄)╭
I just realize maybe the bro developed romantic feelings for her is because he was always away from home, unlike the other bros who was always with her so they treated ber like real sis.