They certainly will interact with each other, they just wont form any kind of relationship. Both Luna and Bastara are kind of outcasts, but Luna wants to be accepted by others, Bastara prefers to be alone (except for Meralin) Still, I must admit it could create some humorous situations.
"Why must this world be lead by silly princesses of love and the sun?!"
"Art thou imply that we are a silly princess?"
"What is your domain?"
"The glorious dark night and the dreams of those who sleep under it!"
"Hmm, glorious domain of the night you say? We might be able to tolerate each other. Shall we stalk the land as shadows..."
"And grant happy and comforting dreams to my subjects?"
"I was going to say slit the throats and shred the minds of your enemies but..."
Warning: may feed off of your love for it.
Depending on how intimate you wanted the class to be I could actually homebrew it.