The Child of the Seventh Month
19 parts Ongoing A 'Voldemort raises Harry Potter' story with the twist of one Neville Longbottom.
Long summary:
Lord Voldemort, aware of the prophecy predicting his demise, captures the two fateful children in order to observe their development and get rid of the threat as soon as it reveals itself.
The two boys, Harry and Neville, are brought up as brothers under Voldemort's watchful eye. While Neville grows up to resent him and love his only family, Harry grows up in an unhealthy infatuation with the Dark Lord and jealousy of his brother.