 If you liked
Otouto ja Irarenai!!
|
 ...then you might like
Kyoudai no Rule.
|
A light haired younger, happy-go-lucky boy is in love with his dark haired step brother, who values his familial relationships above.
Both manga also have several fun/light hearted moments, so if you're looking for BL manga on love between step siblings, these're a good match for each other.