Disclaimer: I don't own Full House. I don't own Nicky or Alex but I do own their older triplet sister.

This will start inside of Rebecca's womb and then move to Rebecca giving birth. As far as she knows she is having twin boys. Cassandra is not known to them. In this story everyone (including Michelle) is in the delivery room "I think I'm going to be born soon," Cassandra said, "The environment in here is too small to hold me."
"Aren't you scared," Alex asked.
"Not at all," Cassandra said, "I don't believe that birth is the end."
"I do," Nicky said, "I think you're born and that's it."
"NICKY! What a think to say with Cassandra about to be born. You might be a little more gentle." ... Rebecca screamed as a contraction hit. It went through her body like a shock. Labor was hard and nobody could stop it from happening. Nobody could take over for her.
"Okay Becky," the doctor said, "It's time to start pushing. On the count of 3." Jesse squeezed her hand.
"You're doing great babe," he said ... Cassandra couldn't hold on anymore. She began to lose her grip on the womb and felt herself tumbling down the birth cannel.
"What about you," Alex asked Nicky, "What do you think happens."
"I think when you're born you get reincarnated into another womb," Nicky said. They looked and they noticed Cassandra was gone. Each shed tears for their lost sister who was now born. ... "Okay his shoulders are out," the doctor said, "One more push and he's here" Rebecca pushed with all her strength and Cassandra came into the world at 3 AM. Jesse watched with his mouth dropped open.
"Is something wrong with the baby," Rebecca said anxiously.
"Nothing," Jesse said, "We just have a girl is all."
"Hey Michelle," Jesse said, "Come 'ere. Want to cut your cousin's cord?"
"Okay," Michelle said grinning. The doctor showed her how to do it. A few minutes later Rebecca delivered the first placenta.
"I wanna hold the baby," Michelle said.
"We need to wash her off first," the doctor said, "and stuff like that."
"Fish sticks," Michelle said.
"Honey you'll have your turn," Rebecca promised. The pain started again. Now Nicky was starting to lose his grip. ...
"Oh no," Nicky whispered.
"What's wrong?"
"I think I'm going to be born soon," he said, "I feel like-"
"No Nicky don't leave me," Alex begged.
"Maybe we'll see each other in another womb," Nicky said smiling bravely for his brother. ...
"Okay," the doctor said, "The second baby is at the birth cannel. It's time to start pushing." Becky gave 8 good pushes and at 3:07 AM Nicky was born."
"We are so lucky to have one of each," Rebecca said as DJ cut the cord."
"Figures," Stephanie said, "I never get to do anything."
"Oh please," DJ said, "You do plenty."
"Do not-"
"Girls not now," Danny said. ...
Alex cried. He was all alone and he felt himself slipping. Oh well all the better. There was nothing left for him. He lost his brother. He lost his sister. Now he would just be nowhere. He closed his eyes and tumbled into the birth cannel.
"Oh my GOD," Jesse said, "There's another head." Rebecca pushed for 20 minutes. Alex was a stubborn one. Finally at 3:27 AM Alex crept out into the world. Stephanie got to cut the cord. ... Inside the room each of the babies were snuggled in the arms of their cousin.
"I told you there was something after birth," Cassandra said.
"Well you were right," Alex replied, "To me it just didn't seem reasonable but you were right about it."
"I'm glad Cassandra was right," Nicky said, "I would hate to be reincarnated without you guys. In this world we can be together again"
"Jesse," Rebecca said, "This could not be more perfect could it," Rebecca grinned