I just upgraded to the newest update and on my second generation(had 6 generations before the upgrade) and in one of my families, well...I have one little boy who walks slow like when they get ill.

He is not ill, I have checked and his energy, health, happiness is at the highest level,I even had a doctor visit as it was just so odd the other children run laps around him, yet by the time he gets anywhere on his own, there is a new event happening. He has one speed and that is S-L-O-W. Anyone else notice this weird "handicap" with their families?

Check his details screen. Does he dislike running? If so, and it really bothers you, the store occasionally stocks a desensitization kit that will remove dislikes.

Oh yes, it does say he dislikes running. Sorry for the silly question, I was just worried it was some silent illness. lol I will buy the kit when it comes up next, thank you for your prompt reply!