Some more head canon I have for 1987 TMNT.
Specifically relating to family/childhood.
I always use the idea the turtles were mutated as children and grew normally. The original cartoon never made up its mind about this so in my verse, they mutated into late toddlers —about three years old and grew normally from there.
I view that group as just as much a family as the others, just a more private one. They're more likely to be physically affectionate at home, partially because that was the traditional Japanese way and he maintained some of that.
But once Splinter decided these four were going to be his children, he threw himself full force into developing amae with them—a traditional Japanese concept of indulgent, pleasurable interdependence. Was usually fulfilled by the mother but without one, Splinter fulfilled it.
Splinter considers himself to have two roles: Father and Sensei. His behavior and expectations change depending on which role he is currently serving.
The turtles all had childhood names for Splinter. It's rare for them to use them now but if circumstances are dire, it slips out:
Leonardo called him Otou-san or ‘Father’
Raphael called him ‘Papa.’
Donatello called him ‘Tou-san’ or ‘Dad.’
Michelangelo called him ‘Tou-chan’ or ‘Daddy.’
The turtles first language was Japanese and they still slip back into it at times. All of them are fluent and all of them can write kanji, hiragana, and katakana.
Splinter gave all the turtles kanji names or the closest he could find instead of relying strictly on katakana (standard practice for foreign names). He based them off personality rather than direct translation. He made each turtle a scroll with their name which all still have in their rooms.
Leonardo: 賢竜 (kenryū) meaning “wise dragon”
Raphael: 守護霊 (Shugorei) meaning “guardian spirit”
Donatello: 忍耐 (Nintai)meaning “resilient mind”
Michelangelo: 心歌 (kokorouta)meaning “heart song”
