My parents forbid me to marry; what happens if I commit zina?

I am a 23-year old boy and doing a good job in capital of Pakistan. We are only 3 brothers, no sister (reason to tell is there no responsibility of her marriage). I am eldest of all, we are a upper-middle class family. Different people have different kinds of minds, and to be honest I am desperate for marriage because it is my need. I can afford my marriage on my own but my parents do not allow it. I never committed zina in my life, but at this stage of my life it seems I will do someday (may Allah prevent me). What does Islam says in such conditions? If I commit zina, will I be sinful? And what about my parents? Will they be too?