20 C.F.R. § 404.908

(a) Who may request a reconsideration. If you are dissatisfied with the initial determination, you may request that we reconsider it. In addition, a person who shows in writing that his or her rights may be adversely affected by the initial determination may request a reconsideration.

(b) Who are parties to a reconsideration. After a request for the reconsideration, you and any person who shows in writing that his or her rights are adversely affected by the initial determination will be parties to the reconsideration.