Ai team mate not sending enough units

I enjoy playing Age of Empires 2 DE against AI. I am a very casual gamer, so playing online I have no interest in what so ever, and AoE2DE is my way to relax. But one thing bothers me, and that is the AI’s ability to do terrible as a team mate when there are no other AI on the team.
So, I played a match of 2v2v2v2 on hardest, and I have been fighting and defending against 3 different AIs for almost the whole match, while my teammate has barely been holding on against another AI and is slowly getting pushed back.
So I noticed something weird. All the other AI sent several units when they attacked, but my team mate sent only a few. If the AI sent equal numbers of it’s most trained units, which was Mameluke, against the enemy, he would win the encounters since the enemy (Portugese) trained Halbs, Light Cav, and Organ Guns for the most part, but no, it kept sending maybe 1 or 2 at a time. This went on for an hour without any progress.
And don’t think about resources. I sent him plenty, and units he had a good amount of. The thing lacking was the intelligence of sending all of them into battle at once.

I suspect that when multiple AIs are playing simultaneously that they are given different aggressiveness levels. That is, if you play that same game over and over, it isn’t that a particular civ or a starting position wins each time. That makes me think they are given random starting strategies.

I have played 8 player FFA, 4v4 and 2v2v2v2. Only case when I have seen this happen is 2v2v2v2. All other times, they are doing a far better job. Although they don’t send big groups together, they keep a stream going.