try calculate for your fathers dob thru your age and age when your mom/dad got married or thru a memorable bday of your dads e.g. 60th or 50th bday. if anything else fail, contact a local embassy and ask for assistance.
Do you have your fathers' school leaving certificate/any school related document/ his passport...
You May need to dig out his shelf to get some kind of documnet which has his DOB!!!
I know its quite tedious...... anyways..Good luck..
After giving it a thought I think I've got it right. The year was either 47 or 49. But I seem to remember age 50 on his death certificate (He died in 1999. May his soul rest in peace) so I think i'll go with 49. I hope it won't be a big problem if I get it slightly wrong by any chance. Would it?