I think over the years we'll encounter a whole bunch of next generation Simpson children, both non-canonical and semi-canonical, but here's the first - he's firmly in the "non-canonical" camp, being a figment of Bart's imagination.

I see on reflection that I have perhaps exaggerated his head size a little too much, but his slightly elongated head and "futuristic" extra bands on his clothing are the only thing distinguishing him from regular Bart, so we might as well go with it.
Bart Jr is seemingly smarter than his father, perhaps the Simpson gene has not kicked in yet.
This post is part of my "Every Simpsons Character Ever" series. For a list of my rules in this project, click here.