Wanting to adopt my stepson

I am wanting to adopt my dh's 9 yr old son. We have 4 kids combined and his son's mom dies in a car accident when he was 3. He's never known a mother or even a mother-figure, except me. He's by accident, called me 'mom' and the whole family gets along well. There is no blended-family segregation as with other families I've seen. His son loves me and I feel the same way. I want to be his mom, not his stepmom or even his dad's wife. I'm sure he feels the same way. I haven't discussed this with my dh or my stepson. It's not like the mom bailed on them both, she died unexpectedly and we've never discussed how anyone feels about the subject. It's such a touchy subject but then again he didn't really know her and my dh says he's completely over it. What should I do? Bring it up? Suggest it? Ask questions I might not like the answers to? I need some help! If it helps, I'm in Stanislaus County...thanks! Renee