Employer is not letting me go ,even I am ready to serve notice pe

Respected sir, I am a software engineer by profession and living in Hyderabad. One month ago (18th August,2014) I joined a software company but due to some family emergency I can not able to continue work and resigned on 19th Sept,2014.But employer is still trying to hold me and not allow me to go.In my offer letter it's clearly mentioned that "Your employment will be subject to a probation period of 4 months .It's our mutual agreement that during the probation period either party may give 2 weeks notice to terminate this contract of employment ". I told them as my parent's health is not well that's why I cannot continue this job and I have to move to my home town . Actually they are not happy with whatever reason I have provided.But Can not I resign without given proper reason or proving it ?In offer letter ,it's nowhere written that I have to provide a good/proper reason and I have to prove that then only they can allow me to go. Is it possible for them to hold me and will not provide relieving and experience letter even though I am ready to serve the notice period of 2 weeks? sir please help