Let asked 4 years ago

I’m a girl and converted to Islam 1 year ago alhamdulillah. I was in a relationship with an Arab boy before and we committed zina. After I became Muslim i tried to stay away from everything haram and also from him but I became very close with his family. We became friends.
He even introduced me to a boy, with both our families know. He is far away from me so we can’t get married now but the problem is, the two men are cousins and know each other since they were children.
The man I want to marry trust his cousin in everything but he committed 2 times zina with me again, it was kind of forced and I repent to Allah after this and know I stoped the contact to him.
I don’t know if I should tell the boy I want to marry (his cousin) about it or if I close this chapter because it’s already in the past.
And as well I don’t know how to explain him that I’m not in contact with his cousin anymore. He said he trust him like a brother and doesn’t know he betrayed him.