>>10 Probably, yeah. I'm assuming it's either 358/2 Days you got, or re:coded? The story won't really make sense if you start with them since they're both sequels and their role is to fill the plot where there's stuff missing from the "main" games.
I'd recommend playing KH1 and KH2 before touching any of the DS games. Or at least watch the cutscenes online, or something.