4th floor flat owner asking money to repair his house water leakage from the 3rd floor flat owner.

I stay in an apartment. My own flat is in 3rd floor and above to that one of the neighbour's own flat is in 4th floor. In that 4th floor flat, some tenant's are staying. The problem is from past few months, there is a water leakage from 4th floor flat (kitchen area) to my 3rd floor flat (kitchen area ceiling, wash area ceiling, bedroom area ceiling and hall area ceiling). Now when we inform to the 4th floor flat owner, he says the cost to repair his 4th floor flat water leakage is around 1 lakh and asking us to share the half of the amount. or else he is not going to get it repair. We told him that his 4th floor flat water leakage is caused due to tenant staying in his flat. But he is denying it and asking us to pay the amount for the repair. There is no such rule in the apartment records. we gave compliant to the apartment society and they are also taking non-sense and asking us only to pay the half amount. This is totally ill-legal and how can i put compliant on the 4th floor owner and the society ?