Hannigan an haife shi ne a Washington, DC, ɗayan ɗa na Emilie (Posner) Haas, mai sayar da ƙasa, da kuma Alan Hannigan, mai ɗaukar motocin Teamsters. Mahaifinta dan asalin Irish ne kuma mahaifiyarta Bayahude ce. Tambaya: A ina aka haifi Hannigan?
Birnin Washington, D.C.