I’ve been trying to find this manga for months now with no luck at all. The only thing I remember is that it was a shoujo manga, possibly from the mid 00s, and the following scene:
FL was really close to her older brother who recently died, and while on the school roof(?), she finds a boy that looks just like her brother. She calls him oniisan or smth and they kiss(?) because the ML thought the girl was in love with her brother(?) but didn’t know he was dead.
I’m pretty sure the ML is kinda a jerk as well?

Any help is super appreciated!

Adding this info as I remember it:
I think the FL's friend pushed her to talk to the ML initially?
Brother might have died in car accident?
FL has long hair, possibly dark
FL ends up being angry with ML after stolen kiss, realizes that he just looks like her brother but doesn't act like him
FL might actually start liking one of the friends of the guy who looks like her brother?
Read this between 2006-2010 as far as I recall, so I don't believe it came out after 2011?

Hmm?

Kinda sounds like With!! but I read that more than 5 years ago.. so who knows.

Ahhh this isn't it unfortunately 🙁

I'm pretty certain that this was never published officially in English (even by CMX!) and that it was a scanlation :/

Thank you though!

Came back to add a bit of information: there was a scene where the female lead is recalling her brother on the phone and she starts crying.

Any chance it’s Hoshi no Oujo?

https://www.mangaupdates.com/series/fy0j7jd/hoshi-no-oujo