I think he briefly appeared previously in family photos and/or flashbacks - He has dark hair like Mihari and the ahoge was his contribution to Mahiro's genes. Though Mahiro's ahoge has grown much larger as he got older, and even more so when he got lolified - probably just because his (her) hair is longer overall.
There are also cases like Tachibana from Fabiniku, who openly identified as female, but still uses male first person pronouns. I don't know what pronouns would be correct in that case.
There are also cases like Tachibana from Fabiniku, who openly identified as female, but still uses male first person pronouns. I don't know what pronouns would be correct in that case.