In bowl mix 6 peaches, peeled and sliced thick. Add ¾ cup sugar, juice of 1 lemon, 12 ounces blackberries and ¼ cup cornstarch. Let sit 20 minutes. Pour into pie shell.
Prepare crumb topping in mixer with paddle attachment. Mix brown sugar, flour, pecans, nutmeg, cinnamon, and butter. Mix on low until mix is the size of small peas.
Top pie with crumb topping and bake 10 minutes at 400 degrees. Reduce heat to 350 degrees. Bake 30 more minutes. Cool slightly. Serve.