Could potentially join. I have two ideas, since I'm not sure if you'd accept another non-human.

The non-human idea is a lovechild of an affair of a noble and a nonhuman, and thus inducting it in the order might have been the most gracious way to settle the issue (Half-Elf or Half-Giant). 

Even so, the idea of a fairy knight claiming to be THE STRONGEST cracks me up tho.

The human idea is a talented, smart but ultimately self-centered slacker that joined the old-renowned order to get an easy time of showing off in times of peace and woo maidens.