and they reached this point cause of lack of trust and understanding in their lives, so both are at fault.

first suicide itself is a wrong decision. no one's life is so rough that they resort to ending their life. 90% battles are lost in the mind and soul. if they didnt want to be with each other.. then just leave get divorced and move on... why end this precious life ?

Both. I feel to commit suicide itself is the wrong decision. Life is to live. Problem in their life is "Lack of trust". Towards life and towards each other.