first, check if the bank required him to issue a life insurance policy in favor of the bank. some require it. when he passes away, the loan may be extinguished. if none, someone will have to keep paying for the loan to keep the payments current.
I assume your parents are married and don't have a pre-nuptial agreement.
what year were they married? how was the house acquired, inherited or purchased?
if it was purchased during the marriage, a donation to the mother is useless, it's their joint property.
his properties will be inherited only by his wife and children, siblings will not have share. he can donate to the children in contemplation of his death, but this will not have any effect on the loan.
if he has no will, then the law will just apply. his half of the conjugal properties will be shared by the wife and legitimate children in equal shares.