I think the reasons for his behavior may get more complicated since there is a female involved. He may be protecting her, or it may have nothing to do with her.
My male became very aggressive at about 4 yrs. of age, but he was an only caique. There was ALWAYS a reason for it. The reason seemed to be that he wanted my undivided attention all the time. If I ignored him, even if he was out with me, he would become very angry and inflict terrible bites. The only way I was able to change his behavior was to get him on a routine where he is getting lots of one on one attn. He seems to thrive on a routine. I have to cuddle him, kiss him, play games with him, in short interact with him quite a bit to keep him happy. He just eats the attn. up. My conure, in contrast, is happy to sit and snuggle on my shoulder while I do other things. The caique is not. In addition, and this may sound harsh, I hit a point where I could not tolerate the bites anymore. When he bit, I would cover him in a towel or shirt (not his head) to get control of him, and put him in the walk in closet with the lights out, closing the door. He was never hurt, but he did not like this and I believe it scared him. After a couple minutes, I would go back with the towel or shirt, lightly drape it over him so I had control of him, and pick him up. I would snuggle him against my chest. Somehow this morphed into him liking to be snuggled all wrapped up in a towel or shirt. And he will let me do this anytime now. He loves the one on one attn. Also, my caique will be 12 yrs. old this month and I do think that his behavior has toned down due to his age. However, I do not know how to deal with a caique's behavior when there is a parrot of the opposite sex involved. I think you need to figure out the reasons for his anger. I am really glad that I stuck with my caique through all of these yrs., because I am really attached to him, especially now that I can manage him.
This is the best advice I can give:
1. Watch his eyes and body language. If his pupils constrict, stay away. If he starts marching back and fort, neck feathers raised, stay away.
2. Give them the biggest cage possible with LOTS of toys and LOTS of time out. As you know, they need constant stimulation.
3. When he is manageable, snuggle him, groom him, talk to him, take him for "walks" around the house. Let him see rooms he has never seen or the inside of closets or hold him up to a window he never looks out of. My boy loves for us to do this. He loves new things within the safety of the house.
4. Make sure the female is protected. Caiques can be vicious to one another. I almost adopted a caique that had most of its beak torn off by another caique. He could seriously harm her, or vice versa.
5. From what I have read, females can also become aggressive, so I would watch her for signs also as she matures.
6. Love them for what they are - wild animals forced to live in an environment that they are not evolved to live in.
7. Consider a night cage, a dinner cage or stand, in addition to a day cage to help break up the monotony.
8. Remember that in the wild he has no boundaries but in a domestic household, his life is defined by boundaries - cage walls, not being allowed out when he wants out, etc.