Co-obligants role in educational loan

Respected Members, What are the grounds on the basis of which it becomes the duty of Co-Obligant (father) to pay off the Educational Loan? Note-1) The person on whose name load has been taken is not having any job yet and preparing for further studies. 2) Co-Obligant is father. 3) Father has good income. 4) He has bank account of his firm in the same bank (same branch too) with transactions in lakhs.