Technicly speaking the bible did allow divorce for the above reason.
however and this is the part that people get stuck on.
It does not allow for the man or woman to be remarried.
Calling that adultery.
Now I dont think anyone here would deny your cousin should have a happy life at all.
in fact I'm glad he found someone good.
But speaking on a biblical term its sinnful yes
Buit then again I dont belive in Sin myself
The question should be more why is it sinfull to get remarried after divorce?
The bible dosnt state the reasons why things were written as they were it simply st ated it to be wrong.
Does it apply anymore?
I dont know I dont think its ever been followed.