There are 2 books in the Proxy series. The newest book is Guardian which came out in 2014.

1
Proxy

Book cover of Proxy
Knox was born into one of the City's wealthiest families. A Patron, he has everything a boy could possibly want -the latest tech, the coolest clothes, and a Proxy to take all his punishments. When Knox breaks a vase, Syd is beaten. When Knox plays a practical joke, Syd is…
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2
Guardian

Book cover of Guardian
In this sequel to Proxy, we first see Syd as an assassination attempt is made on his life. In the new world, led by the Rebooters, Syd is the figurehead of the Revolution. Liam, an 18-year-old Rebooter, is Syd's bodyguard and must protect him with his life. But Machinists with…