Both of Brabenec's parents are Czechoslovak refugees from the former Sudetenland who fled from Soviet communist oppression in the late 1940s.

[8] At age 18, while attending Mount Saint Mary College, Brabenec was appointed as events coordinator for the City of Newburgh, New York.

Brabenec served as a staff assistant to Orange County Executive Edward A. Diana in the early 2000s.

Brabenec resides in Deerpark, New York, and has two children (Karl and Kimberlee) with his ex-wife, Jessica Ebbecke, to whom he was married from 2005 to 2009.

Brabenec was chosen in a special election held November 2014 to fill the remaining term of Assemblywoman Annie Rabbitt, who had resigned to become Orange County Clerk.

On April 27, 2018, Brabenec confirmed he was considering running to replace retiring New York State Senator John Bonacic in the November 2018 election.

[19][20][21] After careful consideration, Brabenec opted to continue his campaign for re-election to the 98th Assembly District for a third term and he won the general election on November 6, 2018.