i really like this kind of series like sugar family or Oniichan to Issho thanks

Kiken Junai D.N.A.
Oujitachi wa Izonsuru on the more mature side

Nulla in mundo pax sincera
"Always go too far, because that's where you'll find the truth." - Albert Camus

Good luck, although the online translation is a little off-putting - the released volumes are better. And the brother is not the main guy.

Sora Log - Brother with a major sister complex. He's not the love interest though.

Sonan Jyanaiyo

Yoru Made Matenai

Not the same - but A Small World is a lovely story about a young step-dad who has a completely non-romantic daughter-complex. It reminded me of Sugar Family somewhat.

50 Rules for Teenagers
He isn't the romantic interest, though. 😛

Oniichan Control. Although it focuses more on him trying to get over the complex and the sisters brother complex.

Quote from Gamermaster42

Oniichan Control. Although it focuses more on him trying to get over the complex and the sisters brother complex.

Should also mention he is failing horribly at doing so xD. Also kissxsis kinda works. And ayu mayu is a very comedic version of it(protag will remind u of ai kora quite a lot).

Few favs
Comedy:
Kyou kara ore wa!!, Mx0, Angel Densetsu, Skip Beat, Ai Kora, The Devil King is Bored

Romance:
Hana to Akuma, No bra, Shinigami Trilogy, kindan no koi de ikou, Usagi Drop, Threads of Time, Girl Friends

Most under rated:
Kindan no koi de ikou, kyou kara ore wa!.
m0r l83r... maybe >_>

The brothers in Hot Gimmick, Desire Climax, and Chiyou yo Hana Yo have huge sister complexes, but they are not the main story.

The poor girl in the short "Chase 4Me" (Oikakete 4Me) by IBUKI Kaede, the second story in Yuuwaku - Sakaraenai Yokubou, has four possessive brothers.

Rika

Being alone is only lonely if you want it to be.
Staying in lucid delusion for an eternity.

http://www.mangaupdates.com/series.html?category=Sister+Complex