Both the Richard III lists and Tudor lists are allowed 2 Yorkist allied commands...
There is a restriction on these Yorkist allies not have pike but with only the retinue archers as compulsories both allied commands could take 2 Royal Knights and 4 knights give a "huge" number of quality knights in these two lists that cannot be match by the other war of the roses lists.
Is this intentional?
On the numbers the period does see a revival of cavalry warfare across Europe folowing the infantry dominated 100YW - its is plausible that this included England and Richard III's cavalry charge at Bosworth is England belatedly catching up. So for Ricard III and the Tudors the basic principle is plausible.
However, I suspect that Royal knights in these allies should probably not be allowed and the overall numbers may end up a bit high - on the other hand I also suspect you'd end up with a bit of a naff list ...
Indeed, there should be a note to say that the Royal Knights are not permitted in an ally contingent.
Richard