It isn't clear what's bothering you, the relationship or the promotions?
My first thought(thot) :)
I wouldn't suggest going to HR. They are there to defend company interests (against any lawsuits that you file for instance), not yours.
Shift to a different team?
How are two people in relationship working together especially when one of them is in the power of position? It is a case of conflict of interest.
Have a definitive and measurable data of your work. This will help you in getting the right treatment in case you go to a skip level meeting regarding this discrimination