He began working and volunteering for area non-profit organizations from the age of 14; he was a youth facilitator for "The Other America Tour," a social justice public education program for high school students in Wisconsin that was organized by the ACLU of Wisconsin and worked for several years with Pathfinders Milwaukee, a non-profit that provides shelter and support for homeless or at-risk teens.
During that time, he also began volunteering with Tikkun Ha-Ir ("Repairing the City"), an organization that engages Milwaukee's Jewish community in civic activities.
[7] After graduating from college, Brostoff worked as a legislative aide to Milwaukee County Supervisor Jason Haas, then served as district director for state senator Chris Larson (D–Milwaukee).
[8] In the Fall of 2013, Brostoff's state representative, Jon Richards, announced he would forgo re-election to seek the Democratic nomination for Attorney General of Wisconsin.
The district comprised all of Milwaukee's lakeshore neighborhoods, including Bay View, the Historic Third Ward, the University of Wisconsin–Milwaukee campus, and Brostoff's home upper east side.
[10] The overwhelmingly Democratic district drew several strong candidates, including Milwaukee County board chair Marina Dimitrijevic, prominent defense attorney Daniel Adams, and labor lawyer Sara Geenen.
His father is a retired attorney, mediator, and arbitrator; his mother is a social worker and businesswoman in the home health care industry.