DEAR ABBY: My fiancé and I have been together nine years. During that time, we have had our ups and downs. Eight years ago, after a year of dating, we decided to move in together. The following year we got into a big argument because his ex-girlfriend was sticking her nose into our household. (She was also dating his brother.) He moved out that night, but we were able to repair our relationship and decided to live separately for a while.

A month and a half after he moved, I found out she was pregnant. Her due date was nine months from when he moved out. He swears it’s not his child and that it’s his brother’s. I have tried to let it go because I can’t accuse him of lying just because of the timing of her pregnancy.

We were engaged once before, and I called it off because of this. He proposed to me again two years ago, and our wedding date is set for next year. I don’t want to call it off again, although this is still bothering me. He knows I was hurt by an ex-boyfriend who cheated on me in the past, and I think he knows if I find out the truth, I will leave him.

He treats this child like she’s his own, not a niece. He picks her up and takes her out for dinner and to the park and other stuff he doesn’t do for his other nieces or nephews. Should I let it go, or trust my gut? — SECRET OR NOT IN NEW YORK

DEAR SECRET: Tell your fiancé you want him to consent to giving a sample of his DNA, as well as his favored niece’s, to be tested. His reaction will speak volumes. If he agrees, you will finally have the answers you are looking for. Do not go ahead with the wedding until you have that information.

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Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Contact Dear Abby at www.DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.