I've raised many different breeds of pigeons since 1982. At one point I had 370 birds of different breeds. 230 of the were homers of different strains. I bred and raised the 2010 Canadian National Champion in breed Kazan Tumbler. She was a beaut. I've had many blue ribbons(1st), many red ribbons(2nd) and quite a few green ribbons(3rd) in many breeds and many classes and colors. The very first year I raised pigeons I got Reserve Champion with a beauty yellow Old Dutch Capuchine YC(young cock), hence the name Reserve Champion Lofts and the "handle" I use on BYC. That same show also afforded me the right to bring home "3rd in Breed" with a silver Kazan Tumbler YH (hen).
All winter all my birds stay in the 1 large coop, which is better now that I only have 100 birds.(It's still a lot of work cleaning but at least it's confined to 1 loft and the pigeon poop is in one pile instead 7. (ooooo it's good for tomatoes)).
Pigeons are monogamous. Yes, they will breed others if they are caged during breeding/nesting season but prefer to stick the one mate. I had 1 old Bandit line cock and a ash-red Jansen hen that were mated as a 3 yr old(cock) & 2 yr old(hen). They spent 10 years in my lofts and not once bred out of their union no matter what other birds cock or hen were in the loft with them. A falcon got at Sylvia one day in December. It chased and caught her but she somehow got out of his claws made it into the coop. After 3 weeks the wound was starting to heal-up nice but she still couldn't fly properly. ...a darn mink got in the trap and finished her. Buddy(cock) died the following spring with out ever having another mate. I personally like to think his heart was broke.
I have purposely mated different breeds. A Capuchine cock to a Fantail hen is an awesome looking bird with a "hairdo" like dad and not quite as "carriage" as mom. A Spinning Donek cock to a Flying Tippler/Birmingham Roller hen is a freakishly amazing performer. Gimpel Archangel cocks to A) red Old Dutch Capuchine hen and B)silver Kazan Tumbler hen created astounding colors in almost perfect station and carriage of the hens' breeds.
I enjoy purebred birds but I also enoy playing with genetics in a natural way. Like breeding a Holstein bull to Hereford cow or vice-versa.
So to answer your original question...... Sure you can house the together. They will most likely stay true to their original mate(unlike the vast majority of the women I've dated), but if one loses a mate he or she will actually fight the other pair's same sex to have a mate, so the natural drive to perpetuate one's own genetics will cause a "widowed cock" will fight the other cock or a "widow" will fight the other female. Well, I can't be sure that will happen in your loft but I've witness these behaviours every day I've raised pigeons.
Long winded story but lots of info. just like .
I hope this helps