Tom had never realized how small the room was until much of it was occupied by a 2,000 pound draft horse, with a hot and heavy look in his dull, brown eyes. With a snort and clap of his front hoof, Matt made it clear he was ready for some action, whether the room was ready for it or not.
Feeling the pressure, Tom attempted to retreat but only got one foot back before Kate was there with her hands at his lower back.
"Don't fight it," she said before a hard shove forced Tom tumbling forward, coming to land in his hands and knees just in front of Matt's massive chest. Tom looked up, now really seeing the size of Matt up close. "If you fight it, it's only gonna be worse for you."
As if to put a period on the send of the remark, Matt moved forward, forcing Tom to duck, only to face that massive head of Matt's horse sized member.
"Oh, no, please," Tom said, gulping at the sight of the massive member in his face. Tom quickly spun around but Matt was on him, pushing his now pre-cum dripping onto the ass of Tom's pj pants. This caused Tom no end of distress as the muscle of the horse was now practically pinning him down before his forelegs.
"That thing looks nearly 2 foot long, kid," Kate said, hands on her hips. "You either give in to what he wants or, well, I don't know where he's burying that cock in you but he'll fit it."
With the cock pressed against his rear, tears streaming down his cheeks, Tom said with some defeat in his voice, "Fine! I wanna be a ma-ARR-oh gooOOAWWWW," but before he even finished the sentence, his face was pushing out and a numbness spread to his fingers and toes.
Matt pushed his cock into Tom's ass again, which was returned with a swell of girth, nearly spreading the seam in the middle. Tom dug his fingers into the carpet, soon bringing them together in a fist that began taking on a heavy, black feel. As Tom struggled to comprehend it all, Kate came over to move Matt away.
"Give him a moment to turn into a proper mate," she said, petting his mane and looking down as Tom's ass swelled again, this time ripping the damp material. He was now sporting a growing tail, puckering equine asshole and a new wet slit to match, just above his shriveled testicles. This event was lost on Tom as he felt the formation of two teats as his waist that began his new udder.
Tom moved, so swayed his ass and tail, causing him to moan mournfully for the loss of his hands to thick hooves. He tried to not think of horses, to think of his own body, thinking that may help. Instead, urged on by a hot smell in the air he could taste, Matt trotted over to Tom, licked his ass once, then proceeded to mount the still undersized rear.
"Matt! Not yet! He's-" but Kate's words and attempts to hold back the massive horse were in vein and Tom was soon feeling the press of a massive cock at his new slit.
"Ogh, oh Godg," Tom gurgled as the massive cock head of the horse forced its way in and sent a jolt through Tom's entire body.
With every inch pushed in, slowly, Tom's body expanded and grew to take it, if only just. Ribs cracking, ears pointing, feet morphing, and posture as a four legged mount are locked into place. He desperately wanted to shut his eyes but the strain of his changing face made it impossible. So Tom was made to watch his out snout form, cheeks puff out and a chestnut dapple coat of fur grow in.
"That's it, Tom. Keep taking it. You were born to take horse cock I think," she teased as his Tom's body and legs finally grew to the size of fertile brood mare. As his neck grew, Matt finally buried himself to the hilt, his heavy testicles bumping up against Tom's udder in a moment neither boy had seen coming only an hour ago.
His neck grown, old hair shedding away as his new mane and horse head finish, leaving on his mind the last bastion of any humanity.
All his mind was enthralled, partly by choice and partly by force, by the sensation of all that stallion in him. There was even a moment where he squeezed his new vagina, gripping the cock, but this only caused the inevitable, and left Tom with a last moment of humanity being the most embarrassing; his stallion roommate had now pumped him so full of horse seed, there was no way he wasn't pregnant. That though, and the subsequent pregnancy and and birth, was enough for the mare to take over completely.
Good thing too, as Tom was spared the feeling of Matt slide out at last, leaving his rear dripping and despoiled; the excess cum staining the remains of Tom's clothes.
Kate placed a call to uncle that he had likely 3 new horses to add to the stables.