Article 21 of the indian constitution.

After going through your query, I understand your condition and here I am to provide you with a piece of advice that might help you out:
Being an adult, you have the right to do whatever you want to do, and having a live-in relationship, which is subsequently legal in India, you are doing no wrong and nobody has the right to stop you from exercising your right to life mentioned under Article 21 of the Indian Constitution. 
Adults who are in a live-in relationship are protected by Indian Laws as per Article 21 of the Indian Constitution, which tends to tell us about the fact that their choice to cohabit without marriage is safeguarded by the Right to Life and Personal Liberty. You can refer to the Supreme Court case of S. Khushboo v. Kanniammal & Anr. (2010) as it has affirmed the legitimacy of live-in relationships, stating that they should not face threats or intimidation for such personal choices.
For this, you can file a complaint at your nearest police station to seek protection under Section 503 of the IPC (which covers criminal intimidation) and Section 506 of the IPC (which provides penalties for the ones who are threatening). 
You can also seek protection orders from family interference and harm under the Domestic Violence Act 2005, to ensure the safety of you and your partner. 
I have provided you with all the provisions of the Indian laws applicable here in the situation. You can file the case against your family as you are an adult now and doing no wrong

Disowning one's son/daughter is unknown to law. Of course, the parents can ensure that all their properties are disposed/bequeathed during their lifetime that there is nothing left for you to inherit.

And our country is governed by rule of law. No one, irrespective of their status, is authorised to take law in their hands.

As rightly observed by expert Mr P Venu, disowning a child by the parents has become a fashion these days though this concept is unknown to law.

However if you feel threatened then you can very well seek the protection through police or any law enforcing agency

If you are major and want to marry anyone legally there is no bar, but morally you need to listen your parents.

Now if you are decided to live your life then you should bear the consequences, your parents self-respect and  emotional attachments are hurt and they can oust you from their emotions and property too