As the siblings are running and getting closer to their fence, the wind picks up causing the top of the trees to sway with each gust. The storm seemed to build in intensity, the rain starting to pelt them with wind carried sheets, slowing their pace.
Jacob can feel a great pressure building inside of his shoes as he is running behind his sister. Looking down in time to see them explode apart, with the middle toes on each foot expanding and his toes fusing together hardening into hooves, allowing him to start running faster. “What's happening to me?”Jacob cries.
“I don't know, we are almost to the fence. Hopefully Dad will know what to do.” Sasha yells through the heavy rain pounding down around and on them.
Jacob feels a pressure forming on his tailbone, prompting him to grunt and whinny when it starts growing in length and long dark brown hairs start growing from it. Prompting Sasha to turn and look. While doing so she gets distracted by her brother's growing equine tail and trips head first over a large field stone.
Jacob running not too far behind her falls on top of her. His long equine penis rubbing against her pussy as it slides between her legs.
Sasha doesn't want to admit it but she is really turned on by this. It seems like she isn't the only one as Jacob starts thrusting, likely overwhelmed by the transformation and lust, rubbing his long cock between her legs. A moan escaping her mouth. When she looks back at her brother, she can see brown fur starting to grow across his body and his nostrils starting to flare as his nose starts to change.