"By one of these studs," Olga said, gesturing to the stallions that were eyeing Iris eagerly. "The two of you may decide between yourselves which one."
"No," Mikhail said firmly. "Iris is my fiancee. If anyone is to impregnate her, it will be me."
"To guarantee our Horse Magic fertility spells work, the two of you need to be in horse form," Olga warned. Mikhail tossed his head.
"That will be no problem." He wasn't as skilled at shape changing as his beloved younger sister, but as the one primarily in charge of the breeding program, Mikhail had to be able to take a horse form. Which he did, becoming a stunning palomino Witch's Pony stallion. He heard some of the Horse Witches nearby gasp at his quality. As the newborn foals were led away, the Horse Witches cast fertility spells upon both Iris and Mikhail. Then Olga stepped forward.
"This will help the two of you," she said. She waved her hand. Mikhail felt a sudden wave of what could only be called horniness wash over him. Iris eagerly moved her tail aside and wiggled her rump, presenting to him. Mikhail didn't need any further invitation. His mind was lost in the desire to mate, to impregnate, to dominate the mare before him. She wasn't the transformed Crown Prince. She was Iris, his mate. Mikhail mounted Iris and plunged his cock deep within her. Mentally, he focused upon taking her as his own, dominating her and claiming her as Witch's Pony stallions did with their favorite mares.
With a deafening whinny, both horses came. Mikhail shot load after load of his seed into Iris's newly emptied uterus, then dismounted her. A quick scan revealed that the mating had been successful. Iris was pregnant with triplets. Mikhail looked at Olga, the mating rush now gone.
"Why was it necessary to do this in horse form?" he asked her.