Johnny Zest is likely Dudley Landgraab.
Johnny's lifestyle and background has some similarities to that of Dudley Landgraab. They both are disowned by family and live in trailer homes within a sand-covered region. The main difference is that Johnny is career ambitious, while Dudley is not.
In the The Sims 2 (console), he is mentioned in a chance card in the Culinary career as a rich kid with hoodlums. He may have been the inspiration for the character of Johnny Zest in The Sims 4, with whom he shares his background, and whose house is very similar to Dudley's; considering that "Johnny Zest" is the character's stage name, it is even possible that Johnny is actually the alternate timeline version of Dudley. Dudley is the only sim who likes being karate chopped.
I have a feeling Don has Bella somewhere in TS2.