Found Rs 2000 notes in my grandfather's cupboard

My grandfather has dementia. He can't remember where he kept his belongings & sometimes he has problem recognising his near & dear ones as well. I found Rs 2000 notes (Rs 2 lakh value) in his cupboard hidden under his documents. He can't remember since when he has kept these bundle of notes. I am based in Mumbai. Where can I deposit these notes? Banks are refusing. Will RBI accept such huge amounts of notes (100 notes)? Which RBI office should I go? If I deposit in my bank account, would I have to pay income tax on this? Or is my grandfather liable to pay tax? Kindly advise. TIA