The Patterns make sense.

OHMIGODS THE PATTERNS.

Okay, epic rant here. Well, more of a physiologic rampage on I KNOW SCHIST.
-THE QUESTS-
Okay, let's start with PJO. Book 1: Percy, Grover, Annabeth. Boy, Boy, Girl.
Book 2: Percy, Tyson, Annabeth. Boy, Boy, Girl.
Book 3: BREAKS THE CYCLE. Percy, Grover, Thalia, Bianca, Zoe. B,B,G,G,G.
Book 4: Percy, Tyson, Grover, Annabeth. B,B,B,G.
Book 5: Breaks the cycle, which focuses ONLY ON THE PROPHECY, aka Percy.
Why am I rampaging on this? Well, here's why...
Heroes of Olympus.
Book 1: Jason, Leo, Piper. Boy, Boy, Girl.
Book 2: Percy, Frank, Hazel. Boy, Boy Girl.
Book 3: *CONFIRMED* Annabeth, (Percy?), (Jason?), _______.
HOLY CHEESE IT'S OBVIOUSLY A GIRL. So yes, I'm done know.
So seriously, I think I have ultimately proved the character either has to be the Hazel, Piper, or the new character. Narrowing it down! Who do you think it is NOW, given this info?

Call my crazy, but I see patterns everywhere. EVERYTHING CONNECTS. I don't care how random it is, everything has to be influenced by something else.