OK... me and my fiancé are planning to get married we been together for 6 years... last November we separated for a few months and now we are back on track... a few days ago we were confronted by a woman saying that my fiancé was her baby's father.. without my knowledge or his... he did say he was with her when we separated... but didn't know anything about her pregnancy... she has given her baby my fiancés last name... we are planing to get a DNA test done... but my question is can she do that without his knowledge of the pregnancy or her giving the baby his last name... hw do I go about this if dna test is negative or positive??

She could have named the child Brad Pitt if she wanted to. A name has nothing to do with paternity.

How to get a DNA test... she will file for child support. Your fiancé requests paternity testing. If it comes back negative, that's the end of it. If it comes back positive, he pays whatever support is ordered and requests whatever custody/visitation that he wants.

If she does not file for child support, he can file for proof of paternity and ask for a court ordered DNA test.

In the end, you were not together, at that time both free to see, date and sleep with others.

You keep saying without his knowledge, I would assume he knew he was having sex with someone?