Source: http://www.nintendo.co.uk/Support/Parents/Hardware/Nintendo-DS/My-children-have-more-than-one-Nintendo-DS-system-How-do-I-find-out-which-games-they-can-play-together-if-we-just-buy-one-copy-of-the-game-/My-children-have-more-than-one-Nintendo-DS-system-How-do-I-find-out-which-games-they-can-play-together-if-we-just-buy-one-copy-of-the-game--659636.html