I've never been monogamous. It might happen, but it never has yet. I don't understand women, I'm off that kick.

The youngest of six children he has four sisters Andrea Colette Elise and Theresa and a brother Nathan. Personal life
Kartheiser dated his The Hairy Bird co-star Rachael Leigh Cook for four months in 1998. Kartheiser later landed a regular role on the supernatural drama series Angel in 2002.