Be careful. If he's accepted paternity of the child and sees her as his daughter, then he may not want to know if she's biologically his or not. And it may not let him off the hook for child support, either.  If you can't learn to accept her as his regardless, you might want to leave. It's not fair to demand he do a paternity test on a child he loves and cares for.

I agree with Tog, if CS has already been awarded and he is on the birth certificate, it might not matter if he is the bio father or not. Besides, if he loves her he may not want to know the truth. I honestly don't think that either of my SS's are actually DH's kids. 

BM1 was whoring around and she was only a one night stand but DH married her because he thought he had to do the right thing. He was 18 and just signed up for the Navy, BM saw: Emancipation (she told him she was 18 but she was really 16, he didn't find out until she tracked him down to tell him she was pregnant), her own house, a car, money- you know all the dependa things. 

BM2 and he rushed into a marriage after a couple of months of long-distance dating. SS15 was supposedly a honeymoon baby- yet he was born 6 weeks early weighing over 8 lbs.... sure DH, he was a premie. 

He loves those kids and it doesn't matter. He sees himself as their father and that is all that matters. 

I also agree. When these situations arise, my advice is to be the listening bystander in the conversation with DH and not a participant. Your opinion should not matter. It is between DH and SD. Stop "pushing" him to get a test. Let him make his own decisions. Six years is a long time to be a father in someone's life; you can't just shut off the tap and call it a day when the DNA test comes back saying he's not the father. 

What is your end desired result here?  Do you expect him to get a test.. then if the child is not his.. never see it again and get out of paying CS?  That may not happen even if he is not the child's father.  What does your husband want?  Does he love his child (or the child he believes is his)? 

What a child looks like is not always a certainty,, I would have sworn my YSD was not his.. but when she got into her late teens.. you could see the resemblance.. it just wasn't apparent when she was a younger child.

Does he even want a paternity test? Maybe he already knows, or has sneaking suspicions and has decided it doesn't matter.

My opinion may be different than others.

I believe kids should know the truth..especially about parternity.