Why couple with same character argue always ???

Some couples with the same character argue always because they want to compete with each others principle or belief. There are cases wherein couples that are both intelligent may fight or argue because no one wants to be defeated by the other especially if the issue is very interesting or that which affects them both. There are even situations where in they are being compared in terms of achievements. Sometimes couples who are both sweet, thoughtful and caring are arguing because they might find their partner lacking one of those characteristics sometimes. I mean if one partner did a sweet thing to his/her partner and he/she did not get the same care then they will argue. Let's say both are caring to their families, they will argue if they can't decide where to go when in family occasions like Christmas.

I think that a couple with same character will always be interisted in the same thing ,however,they will have different opinions,when they discuss together ,they will probably argue ! What do you think of my explaination ?

I have no idea. My guess is because they do the same thing all the time that they get bored. I think people like this should try out new things in their life to make it more exciting.