Sonan Jyanaiyo
Shizuka has always been pampered by her two tough elder brothers Tetsu and Retsu, who are both in love with her. They all 3 know that one of them is adopted but we spend the entire manga trying to figure out who. We also follow Shizuka's emancipation. I like this. The mom is hilarious.
Ichiban Chikaku De Koi O Suru
adopted brother in love with his straight brother. 1 read is enough. Total of 3 chapters.
1st Kiss – I Don’t Want To Consider You As Sister Anymore Webtoon
She's an actress. Her Adopted brother, siscon, jealous of her co-stars, enters in showbiz too, so as to follow her in her world. Lot's of jealousy ahead. Good love tension. Some kind of family drama story is behind it, but to understand it you would need a better translation. Anyone up for a re-translation of the first 31chapters ? Thanks.
Uchi no Otouto-domo ga sumimasen