sat shri akal beta ji .
basic thing is what will be role of religion in life of you both after marraige , if for u as well as him religion is secondary to many other thigns then it is nt such an issue .
In sikhism marraige is union of two souls who decide to walk together on spiritual path , so in that sense it will help if you both have same thoughts on important issues of life .
Ask him what is the basic reason why his family is not ready to accept you as i agree hinduism and sikhism are different religions but a u said u r punjabi hindu so it wont be difficult for you to assimilate sikh values .
A very good article on the issue of inter religon marriage is http://sikhinstitute.org/teach_heri/39- ... youth.html
please go through it once .
Feel free to ask if u hav any further query .