It’ll still be near impossible since parents are living elsewhere and he’s a dependent. It’s nowhere near as easy as it seems. In fact, based on what OP said, it won’t happen.
The way to look at residency at its most fundamental is that your wishes and the UC’s wishes are diametrically opposed. You want residency; they’ll leave no stone unturned to deny residency. Always keep that in mind. They will leave no stone unturned.
OP needs to talk to a residency specialist at the UC. Additionally, being deemed a resident for financial aid purposes, or for a community college are not calculated the same way. The UC has a much more stringent set of rules.