Dudley may well develop beyond his parents. Sometimes it only takes a single life changing event -- certainly his encounter with the dementors would count for that. While in the short run, we saw that Dudley needed to change, he may well have changed greatly in those 19 years. Perhaps he and Harry even became good friends. It would be nice to think they could laugh and shudder together over Harry's treatment during all those pitiful summers.

It would have been so easy to have killed off Percy don't you think? I could have done it in a heartbeat. I think if JKR ever does any subsequent writing that Percy could provide some of the comic relief that F&G did in previous books.