I saw Dear John for the first time on Christmas night and looked up the show information. It turns out long-time Boy Meets World and Girl Meets World star Ben Savage played Judd Hirsch's young son who lived with his ex-wife. He would actually be recast by someone I hadn't heard of (Billy Cohen) in the 3rd season. This is the 2nd time I've seen Ben in a pre-Boy Meets World role, he guest starred on his brother Kevin's show The Wonder Years. The odd thing is I didn't realize it was him until I saw the cast list.

Yea I remember him on the show. He was a semi-regular during the first 2 seasons.

Ben Savage on Dear John as a 7 year old in 1988.
https://www.youtube.com/watch?v=OSG9ZZychLY