Landlord not accepting rent and sent notice to for eviction

Original tenant and his cousin brother were living together for over 3 decades, original tenant made a will in favour of cousin brother, original tenant expired in 1996 and in 1999 his legal heirs went to another flat, giving the possession to cousin brother ... Cousin brother started paying rent by cheque to the landlord he also promised to change the rent receipt in his cousins name but kept delaying and dint.. He's been accepting cheque since past 15 years but dint change rent receipt and now sent eviction notice... What can v do ? Showing reason of sublet...