Any reasonable grouping of Digimon. But you should talk to the DM for what a reasonable grouping would be.

Not to be a rules lawyer, but you'd need minimum 130 Generation for that if my math is right and the two Features require the same families. Near 200 for four Families and two 50 cost features if memory serves. And I don't think being confirmed as a one of [i]the[/i] Royal Knights should be easy, no idea on how you'd get a Digimon confirmed for two.
As an aside, I sense a disturbing pattern, but I do wish ever so much to be proved wrong. Please tell me no one's gunning for something as obviously overpowered as not only a Holy Knight Class Digimon, but one of the Royal Knights this early on, before the game even starts, enough to metagame. Alack, alay, say it isn't so! Say it's just coincide!
[End admittedly over-dramatic aside. Enjoy the rest of your day everyone.]