You don't have to explain yourself at all, or answer to anyone. You're happy. Your feelings require no justification. It's a mistake to try to reconcile what you feel with a social classification, because the classification may not really suit you. You start with your feelings, understand them and be comfortable with them. You, your feeling, and the people you care about are the important things. You're getting in this unnatural, inverted position of trying to explain yourself. You don't have to explain yourself to the world. You just are, and your relationship just is. If other people want to understand it, then you try
to explain to them in basic terms what you feel, and that you're happy. 

Here's how we deal with some specific questions:

"Are you seeing my daughter or this other girl?"
I'm seeing them both.

"So you're cheating on her?"
No. They both know; we're all friends and we're happy that way.

"Well, which do you love?"
I love them both.

"Which do you love more?"
I don't understand the question. They're different people. How do you measure?

"Why don't you commit to one of them?"
Why can't I commit to both of them?

See? You don't have to bend over backwards to express yourself in their terms. They may have to learn your terms to understand you. You're not the one who doesn't understand; they have to put in the work to comprehend you. Remember, the bunch of you have something that comes naturally and feels
right for you; whether or not other people get it is a secondary issue. As long as you do what you want you'll be happy.