(okok so im basically making my own story with inspiration from previous shows and iterations because funsies, and like, idk i have some interesting story ideas ig)
OK BACKSTORY SO BASICALLY
There were two boys in this ninja clan, the foot clan. Hamato Yoshi and Oroku Saki (or what will later be known as Splinter and Shredder) they basically grew up, learning how to fight and stuff. Yoshi was tooken in later, about 14-15 where as Saki had been birthed and raised there. Eventually they became like SUPER close, and they fall in love. However, because of the stigma behind homosexuality at the time, they were forced to keep this secret. They continued to serve the clan. Saki ended up being such a good fighter, that soon he became the leader. His main priority, was to gain more power and expand as a clan. He wanted to do this with force, but Yoshi didn't agree. Saki knew that they'd never see eye to eye, but he still loved him. Eventually Saki comes up with an idea to create a plan without Yoshi knowing. He discovered this scientist named Baxter Stockman. They decide to run some experiments, mutating a few animals to use as weapons later. Many of these mutations didn't work, as many of the mutants became more or less wild and untamed monsters. However, the one that did go right, was a turtle. She was able to listen and comprehend as a human child would, but also had many of the advantages the turtle side gave her. Saki decides to go further with this plan. He gathers 7 more turtles of different species, for different traits, and mutates them as well. they were a success. Soon after, Saki kinda becomes attached to these turtles, he saw them as his children. He even named all of them. 1st, jennika, the first successful turtle. 2nd and 3rd, Venus and Leonardo. 4th and 5th, Donnitello and Raph. 6th and 7th, Mikey and Lita. Lastly, the youngest, Slash. He went down to the lab almost everyday for about 2 years, caring for them as a father would. However, Yoshi finally becomes suspicious of his activity. He follows Saki one day, and finds out about Saki's plan to use the turtles to train and to fight. Yoshi decides the best solution would be to steal them, and hide them somewhere Saki would never find. After Saki falls asleep one night, Yoshi sneeks into the lab. He quietly takes all the turtles (who were all pretty young and freaking out). But just then... the alarms go off. He'd only gathered Jennika, Leo, Raph, Don, Mikey, and Slash. As he ran in a frantic hurry, he fumbled, dropping slash, and spilling the mutagen on himself. He mutated into a rat, meanwhile, Slash was left behind. Saki learns about what happened from the gaurds. His lab was runied. The rest of the turtles there (venus, lita, and slash) were scared shitless. Slash ended up loosing a leg, because of how Yoshi dropped him. Saki became FURIOUS at Yoshi. 1. for stealing his creations, his pride and joy. 2 for abandoning him. Saki goes out looking for Yoshi, his rage growing more intense by the second. No luck. Yoshi goes into hiding in the sewers, not like a rat can integrate into society that well. He starts going under the alias of Splinter, as to not get found by Saki, who was now going by Shredder. Shredder continued to grow his army, and train his turtles. Not only just to fight to expand, but to get revenge on the man that took everything away from him. The man who broke his heart. Yoshi. Meanwhile, Splinter knew of this, so he trained his turtles to fight as well, so they could defend him, themselves, and others.

anyway that's mostly it. i might change some stuff, but idk. any thoughts, questions, deep ponderings, critiques, or ideas pls tell me :p