The Heir and the younger siblings in blood and in all but blood

Harry Potter are the older brother of a set of triplets, Rose, Emma and Nick Potter, in this story, but they are all four living at Saint William's Orphanage, with Dudley Dursley, Neville Longbottom and Draco Malfoy, Parings: HP/DG, DD/SB, DM/AG, OC/NL, OC/BZ, OC/HA, HG/RW and GW/DT, Bashing: MW, PW, RW, GW, HG and the Dark for Draco, Mentors: FF, MM, AD, SS and PS.