My dogs have been battling for alpha position for months, what do i do?

i have 2 bull terriers, same age, same litter. the female we rescued at 6mos old and have had her for 3 months now. the boy we rescued maybe 2 months ago max. Dextor began to try and express his dominance by humping DeeDee, and she then bites him, but he won't stop trying. they are constantly doing this, the only time they are quiet is when they are both in their seperate crates. Dextor also is a marker. How can I get my dogs to finally establish a pecking order since they have not gotten it settled yet?