Dr. Naik,
I'm 24 years old.
I had a relationship with a gut for 4 years. We lived together.
But I never loved him. Now I'm asking to Allah for forgiveness.

My family is looking for a guy for me.
If I want to marry someone should I tell him about my past relationship?

Honesty is one of the main pillars of a relationship. It is essential to share however you need to keep it moderate, and not go into to many specifics. If you start talking about it, keep it short and simple and if he starts asking to questions try and evaluate the questions and you only can know if it is appropriate to answer or not. Don't answer questions that might make him unconfortable or can have impact on your new relation.

Allah ma3ak

YES, Absolutely!!

Depends on the rules of your culture. What are the possible negative results of telling him? Of not telling him?

It depends on if u think u will stay with him 4 ever or not. And it also depends on what will happen if u tell him Good luck hope u make the rite choice. Sorry I couldn't help out more.