in country music why did these two duets break up.?

brooks and dunn retired, not a break up

Big was recovering from a neck injury and rich recorded without him with Big Kenny's good wishes.

Brooks and Dunn went their own ways to pursue different things, as mentioned above.

John Rich and Big Kenny Alphine(sp?) did take a break due to a neck injury Big Kenny suffered years before. Both of them recorded a solo album in that seperation time. They are now back together touring with Gretchen Wilson and I believe one other act and do plan on recording/releasing another album together as Big & Rich

... i am guessing on Big & Rich but i believe it was over billing rights and Brooks & Dunn they felt they had the run of the mill and wanted to do pursue other things

I don't listen to spin. The reason duets break up is because of money.

Because one is more pig headed than the other, and the reason they get back together is because of one reason. Money again. Eric.

They retired