Remember, Secret of Sam established that Grace would enjoy a scenario where everyone lived together and slept together on a giant bean bag.
I would still not surprised if the pseudo-poly relationship stuff leads to Grace's uryuom child later in life. just...an overpowered child of all the characters, it would be so in character for her. because all this connection has to lead up to something and if they're comfortable enough with it, it could happen.
My Fan Fiction: To Catch A Mew
A Kalos based pokemon fan fic. Now up to Chapter 25!