If you are with your ex I doubt that your family will disown you. They may just be very unhappy with you. You can't separate his lying from him as a partner. You have to take all of the information about a person and accept all of it. If you take him back you take the lying back. People often forget that when you reunite with an old partner all the problems are still there. We tend to romanticize a partner thinking that it will be better next time. That often is not the case. He can't be perfect and a liar.
You have to do what you think is best. This is no one else's decision but yours. If you think you can tolerate the lies then you can accept the relationship. If you do decide to do this then you have to stand up to your family. You can't lie about this so you have no choice but to tell them that you are going to do what you want to do. You may want to take their reactions into consideration. Do what makes you happy!
Please press accept; this is the only way I am compensated