It seems to be a new symbol with the logo so it makes me think it's not related to any enemies we currently have or any allies. The word king stands out the most to me. Fallen have their leaders like Archons, Primes and Kell's. Vex have their axis minds. Hive have crota, oryx and God like leaders Cabal have their commanders. No enemies have used a monarchy referring to having a king. So it makes me think that it's in relation to the awoken. The only time we've heard something similar is the awoken. So maybe the Taken King is the queens dad and he went missing so she took over? Please correct me if I've got facts completely wrong. I haven't read every bit of grimoire but it's a theory that seems like something to me. Edit TL;DR - I believe it's related to the Awoken. Where there's a queen there's a king. Edit 2 To all the people saying about the awoken matriarch. I'm thinking it may have not always been that way. Maybe the current queen wasn't always the queen and she took over when the king was taken and made it a matriarch society