Castillo and partner John Pennycuff are partners in life and activism, seen at protests for Queer Nation, ACT UP, anti-violence, pro-marriage, and much more. They have made headlines for being arrested dancing together and at rallies, and were first in line for the Cook County domestic-partnership registry. They flew to San Francisco to be married during that brief opportunity, and plan to take advantage of new marriage laws there. Castillo is also active on Latino issues.