YA book about a boy set in a “utopia” society in a dome. Read around 2012. Spoilers ahead.

[Hannah]

I read this book around 2012. It was about a boy whose family either founded the city they lived in or was a big part of it’s development. I want to say the city was in a dome. The boy didn’t think like the others and he got along with his grandfather. He was playing outside and saw an opening in the dome, I think someone was in the opening, but I’m not sure. Spoilers ahead! His grandfather died and his older brother or cousin who had it out for him kicked him out of the dome city, or he imprisoned him and the kid escaped, I can't quite remember. TIA!

[Capn]

If you feel like a browse (please let us know what the title is, if you find it!), there's:
"Help! I'm Stuck in a Dome" on Listopia
https://www.goodreads.com/list/show/1...

[Rainbowheart]

Off the Road?

[Kris]

Rainbowheart's suggestion of Off the Road by Nina Bawden look promising.

Google Books has a "snippet" preview. You might get lucky searching for keywords:
https://books.google.com/books?id=9te... There are different cover images.