Jealousy Between Kings by lunamoomstar (a Sonic x Arthur x Lancelot fic)

Once upon a time, there lay three kings in the land of Avalon. A lord, a knight, and a warrior. Combined, the three's union sat above all else. They had a lake of love and understanding. A foundation so strong, not even the mightiest of winds would tear it down.

But... what if something disturbed the sediment. What if... that one force drove the three lovers into a tight game of longing and to belong.

After a dream sparks "inspiration", sonic makes it his mission to keep his lovers nightly escapades at arms length. But, after a while and many unforeseen circumstances later, he finds himself met with a new addition in his life.

However, the disturbance is falling deeper into their lake. And, before anyone knows it, that rock has his sights on one blue tinted bubble. So, he plays his cards until he can call it his own.

(Or a simpler way to put it)

Sonic doesn't let Arthur and Lancelot hit as a 'prank' and makes friends with new royalty. Royalty who wants that blue bag. But sonic doesn't notice and just thinks they're friends. But everyone else can see the new royalty falling head over heels by the second...