Answer: Evergreens do not "spread" like other trees can. Some trees, like sumac, have roots that will sprout and create new plants at some distance from the original plant and can, eventually, create a thicket. Other plants, such as lilacs and crabapples, send up suckers around the base of the tree and can become quite bushy. Evergreens (pines, spruces, etc.), don't spread this way.
However, evergreens do reproduce by the seeds contained in the cones. Is your tree producing "pinecones"? If not, then you don't have any seeds to sprout. (The sprouts you see at your friend's house are likely sprouting from seeds released by the cones.) If you do have cones, but no seedlings, then the area around the tree isn't for some reason encouraging the sprouting and growth of seedlings. Perhaps it's too dry, or too shaded. You might try sowing some seeds from your cones, or your friend's tree's cones, into a special nursery bed and see if, with a little TLC, you can encourage them to grow.
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