i really want the trio to be just that- a trio
but in a hypothetical situation id say Neville.
cuz never mind emotional connections, harry will become much more curious and much more willing to be involved in nev's life after learning of their shared connection.
knowing that another boy was in the same prophecy that you were can do strange things to you- and there's will be a very pecualiar yet close relationship. already harry views neville differently. now with their shared hatred( and im using that word loosely) of bella the cow, they might become close
i wont be surprised if neville becomes the first person harry tells the prophecy to