Was going to make this a cap but it ended up being too long so it is now a very short story.

It was too late. My girlfriend's little brat of a brother had just jumped out of the en-suite shower room and even with a towel covering his modesty managed to snatch the necklace out of my hands. He was running around the room with it. "Hah its mine now. You'll never get it! Just what I've always wanted." he mocked. "Give it back you little shit! That is a surprise present for your sister. The lady in the shop said nobody but Lucy can wear it!" But he didn't head my warnings and it only spurred the teenage troublemaker to put it round his neck. As the boy sat down on the bed, the necklace clasped shut on the chain, it started to glow."Hey Mike I can't get it off now. It won't...I feel..." Eddie was rubbing his temples as his train of thought meandered. His mousy wet hair began to sprawl down his back and he had a fixed expression on his boyish face. It was ever so slightly melting into a softer more feminine appearance. Eddie held his hands out, inspecting them as his fingernails lengthened. His arms so smooth and his skin rippling gently but continuously. I rushed over to him pushed his shoulders back and pulled his face to me so I could get a better look. He stood up, the towel dropping to the floor. He grinned and flung himself at me, leaping up so I could catch him. "Eddie what the ...?" Everything about him was reshaping and changing. I set him down onto the floor and he started to convulse. Shaking and shivering his body parts morphed and shifted. His ass cheeks plumped out a little and his penis shriveled away. I couldn't believe what I was looking at but could not take my eyes of him. A perfectly formed and somehow shaved pussy formed where his penis had just been. He looked up at me and put his arms around my neck. I looked down at him and his nipples were bulging from underneath and protruding into my own chest. Jumping up and wrapping his now smooth and shapely legs around me he squeezed me hard. The bulges pushed outwards, growing and swelling and to finish it off a couple of kinky piercings appeared through his nipples. I could feel my cock harden. And so could he. "This is mine now." he said in a sweet cute little voice. He was referring to the necklace."You naughty boy. This was for my sister so she'd fuck you silly. We'll. I'd like to fuck you. silly!"