I need godly advice from you.
Before I married my husband, he once dated a girl for a few months. They had sexual intercourse with each other one time. All this happened several years ago. My husband and I have been married for a few years now. He is a very truthful and open-minded, so he told me about his past sexual encounters, and I told him about mine too.
Presently, his younger brother decided to start dating this same girl from my husband's past. I can't help but feel very uncomfortable with it. Am I being wicked by not wishing they eventually get married? How do I forget about the issue?
There are many reasons why fornication is wrong and this illustrates one of them. Yes, the situation is awkward. Likely it won't work out because the same reason your husband rejected this woman will probably cause his brother to reject her as well. It would be good of your husband to warn his brother that this woman was a cause of him sinning in the past, but ultimately, it will be the brother's decision.
On your part, just remember that your husband picked you and not her for good reasons.