Adds some junk to the trunk and becomes something new.

Erica move towards John dragged in by the gravity of the strange being that her brother was rapidly transforming into. He wrapped his arms around her neck pulling her to his bosom pushing her face into Melanie until the great fleshy slit began to open. He'd always fantasised about this, about transcending and transforming but most of all he'd fantasised about becoming something new.

He grinned watching as his older sister disappeared down his shaft being swallowed by his perfected python. He gripped onto Melanie sides watching as she swallowed Erica it felt so surreal. Like cumming in reverse he could hear her muffled moans and grinned as she disappeared inside of his balls. He felt Melanie begin to churn and knew that his sister's were now intermingling with one another the essence of Melanie the essence of Erica and his own were beginning to fuse and mingle with one another. He let out another gasp as Erica's features began to mingle with his own. John felt his hair lengthening and knew that the colour was shifting. What a previously been brown was now a mix of red-brown and blonde just as his body began to shift. As his balls began to infuse his sister's very being. He felt his legs split and the second pair begin their inevitable migration backwards. There was so much person to use here. He felt Melanie slipping backwards sliding along his elongated belly as John allowed the transformation to continue. A second set of breasts was swelling out of his chest and now his hips were beginning to flare out. The front of his body was now almost entirely feminine while the rear exhibited more masculine tendencies. His feet lengthened transforming from human to a more bestial shape that better suited his new nature. Between his more delicate front legs felt a searing heat is a brand-new vagina began to open.

John could feel his own identity changing, as bits of Erica and Melanie began to fuse into his new form, into their new form. They grinned. They had enough seed to create two copies of themselves. All they needed was a new brood mare.