Marcus Calder is Lev's older brother and at twenty-eight the oldest of the Calder children. Marcus is introduced in Unwind during Lev's tithing party. During the party Marcus has a drunk outburst in which he calls out his parents for ending Lev's life so early and always making bad decisions. At first Lev didn't know what to think of Marcus's rant but in the next book he states that Marcus was the only person that stood up for Lev's life.
In UnWholly we find out that after Lev's clapper incident Lev's parents refuse to take him, so Marcus takes custody of him instead. A clapper (disguised as a harmless girlscout selling cookies) from the organization that brainwashed Lev into becoming a clapper comes to Lev and Marcus's house to take revenge on Lev for wasting their money by not clapping. When the clapper detonates, Marcus is gravely injured. Afraid of what might become of him, he tells Lev to let the doctors give him unwound parts. Their parents take care of all the hospital fees for Marcus and takes him back home with them, not given much of a choice. In the process they also dissown Lev. Marcus is healed using unwind parts. he recieves a new leg and a big ole penis.