How to practice Metta without a Benefactor?

I find it very difficult to practice metta because i can't find anyone who has been a benefactor.I don't know a lot of people.Most people i know i find it very difficult to send metta to as a benefactor as their either very dear to me or downright hostile.Can i just imagine a benefactor i never had .Or use a dead person, as my auntie was very kind to me but she's deceased now. How can i practice metta without a benefactor? How can i find a benefactor to practice metta to?