I'm trying to find this shoujo manga with about 40-48 chapters
It's about a family with brother, sister, mom and dad. I don't really remember what the story was in the first chapters, all I remember is that the brother and sister fall in love and then the dad dies so the fl says it's a punishment from god cuz they fell in love with each other then the mom finds out and takes her daughter so the fl move somewhere else.Then they met again again a decade.

later in the story, it was revealed that the ML isn't Fmls brother since the father took care of him as his son because his 2 best friends died but he told the fl mother it's his son.

Thanks!

Boku wa Imouto ni Koi o Suru?

https://www.mangaupdates.com/series.html?id=90133 this one?

It is this one!! Thanks, I didn't know it was in the description 😀.