Yeah, I wonder about that. I've looked into D's eyes multiple times and asked that very same question ... "Do you want to be poly? Would you rather be mono?" and the answer has always been an unequivocal and emphatic "Yes, I want to be poly!" and "No, I don't want to be mono!" He swears to me that he wants C in our life, he is fine with C being my co-primary, he wants things to work, he loves having C live with us.