Even in Giant Days, Dean’s age was something of a mystery, with him looking and acting older than he actually was/is. Assuming he was in the same age bracket as the Giant Days cast, he would be about 10 years older than Lottie, which would put Dean in his late 20’s / early 30’s as of Solver.

Related, I wonder if Dean ever made the connection between Lottie and Esther. Lottie was, though her sister Sarah, one Esther’s friends and viewed Esther as her fashion role-model, while Dean viewed Esther as his nemesis.