i think its a bit complicated since. roxas while being a nobody. does seem to have a heart. and sora even though he became a heartless. does seem to have a body. and also. sora became a heartless. by stabbing himself with the keyblade if i remember correctly, to release kairis pure heart.
i think the fact that sora has kairis pure heart in him. (which caused namine to be made) and that when he released it causing roxas to be made. something abnormal happened (much like with namine)
since both roxas and namine are nobodies but they are special. in thinking its possible that sora was actually split ito 2. having only 1/2 body soul and heart in both him and roxas. course i could be totally wrong.
this could be why roxas had 1/2 of soras. power and why he could use the keyblade also.
i think the fact that sora has kairis pure heart in him. (which caused namine to be made) and that when he released it causing roxas to be made. something abnormal happened (much like with namine)
since both roxas and namine are nobodies but they are special. in thinking its possible that sora was actually split ito 2. having only 1/2 body soul and heart in both him and roxas. course i could be totally wrong.
this could be why roxas had 1/2 of soras. power and why he could use the keyblade also.