Yeah, ok. Not many characters in Disney aren’t youthful. One that definitely springs to mind is UP! 

After loosing his wife Mr Fredricksen forgets how to be happy how he was in his youth, and even just before his wife died he was still loving life and planning their special trip to Paradise Falls. Until one day Russel turns up at his house and refuses to leave (in a very lighthearted, naive, child like manner). Mr Fedricksen eventually opens up to Russel and lets himself feel happiness again