I think you should ask your cousin to install some anti-virus/malware software that will surely help detect if there is any virus or malware affecting the system.
Just looking at the IP as far as my knowledge goes would not help.
Yes he contacted the PS support on twitter and told them about the issue, they gave him a guide and there were reasons listed for ‘why your profile got banned or why PSN is rejecting your Ip’. One of the reasons were about having a spyware, malware or any sort of virus in your computer system that is connected from a same router, PS has some sort of hawkeye that monitors connection. If they detect something smelly on the other end, they just don’t allow their user to enter PSN system.