I ordered one for myself and my son.

I ordered a 5 for me and a 00 for my 5 year old. I tried mine on and found it is narrow (not wide enough) around my torso. I'm a bit thick in the trunk so I figured I probably should have ordered a size 6 top. However when my son tried his on he had the same issue when tying the top together it would be too snug around his middle and he is NOT thick around the middle at all.

I'm 5 foot 9 inches & 210 LBs so I ordered my size exactly. The jacket is long enough and the pants are a bit too long but can be tailored. I'm going to try a Size 6 top and Size 4 pants to see how that combo works for me. Either way I'll have to get my Gi (any brand I get) tailored a bit as I've got a bit of a long torso and short-ish legs.