Kate - There really is no way to tell apart from DNA tests. I'm sorry you're going through this, mistakes do happen and unfortunately you're facing an awful consequence. I hope you come to the decision that is right for you.

Teagz - the OP was after opinions on who the father was most likely to be, not whether she should keep the baby. I'm sure Kate is already agonizing over the decision without being made to feel guilty if she does indeed decide that terminating would be the best option for her.