So I know there's been an "official answer" about that but it just doesn't make sense! So basically, there's this big KH plot hole in the series. DO NOBODIES AGE?! Nomura said no, but Zexion and Naminé clearly aged while they were nobodies. While Naminé can get away with saying that it's because she's a "special nobody" there's no explanation to why Zexion aged. Some people say it's because Zexion had grown into the man he is now when he became a nobody but according to the KH storyline, this can't be true since Xehanort and the other pupils started experimenting on the heart around a year after BBS (since that's when Radiant Garden fell into darkness) and around that time, they became nobodies. You can clearly see in this KH3D scene that Zexion was still a kid when he turned into a nobody, so why did he age?
I think the answer is that Nomura said nobodies didn't age because at that time we didn't know they could grow hearts. I think that any being with a heart can age but a being without a heart can't. It's the only logical explanation to me. That would explain why Ventus didn't age since BBS, because he doesn't have his heart. But if that's not the reason, then the only answer is: NOMURA-LOGIC.
So I know there's been an "official answer" about that but it just doesn't make sense! So basically, there's this big KH plot hole in the series. DO NOBODIES AGE?! Nomura said no, but Zexion and Naminé clearly aged while they were nobodies. While Naminé can get away with saying that it's because she's a "special nobody" there's no explanation to why Zexion aged. Some people say it's because Zexion had grown into the man he is now when he became a nobody but according to the KH storyline, this can't be true since Xehanort and the other pupils started experimenting on the heart around a year after BBS (since that's when Radiant Garden fell into darkness) and around that time, they became nobodies. You can clearly see in this KH3D scene that Zexion was still a kid when he turned into a nobody, so why did he age?
https://www.youtube.com/watch?v=4Fr7a2N3NgQ&index=1&list=PLhcSrKyqhfh65KdZulRZNEEaADPxlkVy3
I think the answer is that Nomura said nobodies didn't age because at that time we didn't know they could grow hearts. I think that any being with a heart can age but a being without a heart can't. It's the only logical explanation to me. That would explain why Ventus didn't age since BBS, because he doesn't have his heart. But if that's not the reason, then the only answer is: NOMURA-LOGIC.