Building up a new floor over an existing floor
 

Upstairs i have a large living room .. has 2x12 joists running across 16in OC with OSB subfloor.
Half of the living room floor is 13in. below the other.
i want to level the floor by stacking a new floor over the lower floor.
Can i simply build a new floor atop using 2x6 joists (will support it every 32in)?

No pictures, no way to know the spans your thinking of running the 2 X6's, no way to know how this is going to effect things like doorways, steps, trim, the distance from floor to bottom of windows.

What does that mean?

Never 32" o/c. Always 16, stacked over the existing 2x12's, as long as there will be support under or close to where the news joists end. It sounds like the existing joists can support the new load, depending what they're bearing on. How do 2x6 joists make up 13"?