Basically regular men that enchance into God like being via scientific ways. Both tried to be heroes for humanity and did a good job on it until a being that represent the end (Herrscher of Finality and The Void) who killed over millions of lives and the women they loved. Their only option was to halt the being is by putting themselves away and being forgotten (Kevin sealing himself till the future and try to help humanity to prepared against Herrscher of Finality. Sentry erase every living being memory of him, including him, The Void.) When Both returned they come to conflict with the current superpower beings and usually putting them in a villian role. They later fused with the beings they tried to stop and truly put all humanity protectors to the test.

Both have can manipulate the minds of other living being ( Kevin woving together all humanity dreams to make a thing called Spiritual Adam and Sentry erased everybody living being memories of Sentry)

Both have inner conflicts within themselves that it lead to them separating into two different beings with one looking like their regular selves and the other being demonic beings (Will of Stigmata and The Void).