He's good friends with Potter, who I believe inherited your house elf from your brother. I'm not clear on the details, but I remember Draco ranting about it. He ranted a lot about Potter.
Longbottom is very much one of Dumbledore's minions. He also cut the head of the Dark Lord's giant snake during the battle at Hogwarts, after pulling the Sword of Gryffindor out of the Sorting Hat. It doesn't get much more Dumbledore's minion than that.