If you're looking for manga similar to Boku no Otouto no Kawaisa wa Ijou, you might like these titles.
A guy gains a younger step-brother named Aoi after his mom remarries, only to discover later that Aoi enjoys cross-dressing.
Having upset the president of the student council and embarrassing her in many different situations, Tsukasa is forced to do a small "punishment" by the president.
A young boy discovers his girlish charms to fight back against his older brother forcing him to crossdress.
Nanami Kousaka wants to be an idol, but he keeps getting turned down at auditions because of his overly cute appearance. He is approached by a producer, Kouichi Kitami, who gets him to debut as Mi-Na while crossdressing.
A very short one-shot story about a boy cross-dressing because he wants to become cute.
Haruka and Kanata's cousin Yuzu is coming to live with them, but she hates men. Enter Haruka's brilliant idea: Kanata should crossdress.