At his age and condition I don't think cibil score drop in not a huge concern it can be recovered.options :
1) Tell your parents - pay all dues in fulllll and then negotiate for cibil reversals- PREFERRED
2) Pay minimum due to start with - speak to bank and start clearing dues over next few months- negotiate a pay plan
3) Negotiate a settlement with banks, close all dues and get cibil masked - most expensive and will take lots of negotiation
Major concern is the amount he has to repay to the bank along with the interest. Idk without income how OP managed to spend ~4L in a statement. Or it's past due pile-up 🤔
Best option is 1. Maar pdegi but issue will be resolved.