Exgirl friend claims she's had my child

What is the name of your state?What is the name of your state? California

I'm married with children. Now my ex girl friend from years ago has asked me for a DNA test. She claims she's had my child because the father she put down on that birth certificate originally has taken a test and it's not his child. So she's saying it's mine. I cant deny if it is or isnt but I do have proof that she had been cheating on me with 2 other men during that time, am i obligated to take a dna test in my state or not?

thank you in advance for your advise.

You have a right to demand a DNA test. If the child is yours, file for shared custody or visitation and establish a relationship with your child, and an opportunity for your kids to know their sibling. Expect that a CS order will be established.