Should I tell my fiancée I had sex with her sister?

Dear Pastor,

I have a problem. I am 25 and I am preparing to get married. Before I became a Christian I did a lot of wrong things. Some people called me wild and a gallis. I have two children with two different women. One is 10 and the other is seven. I had sex with a girl but she had her boyfriend so we decided to do a thing and not to make our love permanent. Soon after, I fell in love with her sister. I thought I was going to just have sex with her and move on but she held on to me. She didn't stop calling me. She did not know that I had sex with her sister and up until now she doesn't know. She told her sister about our friendship and the sister couldn't tell her to leave me so now we are still friends. The problem is, she is now pregnant for me and she wants us to get married. I told her yes but because I had sex with her sister it is bothering me. I talked to her sister about it and she told me not to let what happened slip out of my mouth because her husband would be very upset. I really love this girl who is pregnant for me and since I am with her, I have never tried to get around the other sister. When everybody is together I try not to talk up too much to her sister who is now married. I want an advice from you. Do you think I should tell her that I had a relationship with her sister? The two sisters are very close. Please help me to make a decision.

T.E

Dear T.E.,

Your conscience is bothering you because as a "gallis" you were not careful with whom you have sex. You had an intimate relationship with your present girlfriend's sister. You knew that she had her man so you encouraged her to cheat. Then you moved on to her sister. You cannot say that you did not know they were sisters. Why then did you go to bed with the two sisters? You didn't take the relationship seriously but this girl was not prepared to have you use her and walk away.

It seems to me that when you had sex with her sister who had her boyfriends it was just raw lust but then you fell in love with her sister and the relationship has grown and she is pregnant. The question is, should you tell her that you had a sexual relationship with her sister? My question to you is, what would be the purpose of telling her? Would it enhance the relationship? I would think not. You would only stir up hullabaloo because she is likely to approach her sister on the matter. She might even inform her sister's husband about what happened between the both of you. And her husband might be disappointed in her because the two of them were going during the period you both had sex.

Therefore, sir, you ought to keep your mouth shut. I do not see any good coming out of such a disclosure. Now that your girlfriend and yourself are planning to be married, I hope that both of you would go to see a family counsellor for premarital counselling and that you would seriously accept what he/she says and abandon your old lifestyle.

Pastor