Mrrzy said "ANY animal that has sex, doesn't mate for life (and even then...) and has more than one offspring/pregnancy can have different fathers for the different offspring. You can have sex with three guys (male ones), have triplets, and each can have a different father."
There is a paragraph in today's "Gulf News" about a woman in South America who brought a paternaty suit against a former boyfriend for support of her twins. Genetic tests showed that he was the father of the boy, but not of the girl!