Some TMNT stuff really isn't for little kids.
In the IDW continuity, the children of St. Robert's Orphanage are a group of human orphans whose home was destroyed during the Invasion of the Triceratons, were rescued from being murdered by the Rat King, and have since been given a new home at Foot Headquarters.
Most of the orphans have not been named, and most of those who have been named have not appeared by name in more than one issue.
The orphans first appear in Kingdom of Rats, part 2. The recent war in New York City had destroyed their orphanage, leaving them homeless. The Rat King comes across the ruined orphanage, and mischievously decides to use his flute to lure the orphans to one of the city's destroyed bridges, with the intention of forcing them to jump off the bridge for his amusement.
In Kingdom of Rats, part 4, the Turtles disrupt the Rat King's activities, forcing him to flee. The Turtles take the children to their estranged father Splinter, convincing him to take the orphans into the care of his Foot Clan.
In the Michelangelo Macro-Series issue, a disapproving Splinter privately agrees with his son Leonardo to take in the children to be raised at Foot Headquarters, on condition that they be trained as future Foot Ninja. While Leo and his brothers Raphael and Donatello are reluctant to start another dispute during a shaky détente with their father whom they battled as an enemy during the Triceraton war, Michelangelo, who has had more recent disagreements with Splinter than any of the Turtles, angrily rejects turning the orphans into weapons. That night, Mikey manages to incapacitate the Foot guards and spirit the orphans out of Foot HQ and into the sewers of New York City, with the intent of bringing them to the O'Neil Farm in Northampton where he will raise and train them peacefully, just as Hamato Yoshi had done for the Hamato Children during Splinter and the Turtles' previous human lives. In reality, Mikey quickly finds that he has no idea how to look after so many children on his own. Just as the weight of the situation really begins to weigh on Mikey's mind, he and the orphans are tracked down in the sewer by Splinter, his chūnin Jennika and the other Turtles, and Splinter angrily demands the orphans' return. But a determined Mikey instead hurries to move the children deeper into the sewer and away from his father's reach. After Splinter's continued objections, Mikey faces him and furiously shouts, "Screw you!" Everyone is stunned, and Mikey goes on to denounce his father and his many broken promises, comparing him unfavorably to the Shredder. Enraged, Splinter engages in one-on-one combat with his son, and though Mikey is no match for his father, he stubbornly holds his ground. When Splinter realizes Michelangelo would truly rather die than surrender, Splinter abruptly congratulates his son Leonardo as Clan Hamato jōnin for using his brother to demonstrate their clan's dedication at protecting the city's people. In a face-saving lie, Splinter then feigns that his prior agreement with Leonardo was actually that the orphans would be materially cared for by the Foot Clan but trained in ninjutsu only by Clan Hamato, then when they come of age, will only then be given the free choice of whether to join the Foot Clan. As Splinter feels great shame for taking up arms against his son, Michelangelo had managed to enact positive change both in the professional relationship between clans and in the future of the orphans, ensuring himself a meaningful role in their upbringing as their new sensei.
In a short scene in issue #85, Jennika is trying to organize the unruly orphans for some exercise before their regular training with Michelangelo. Casey Jones arrives at Splinter's request with vanilla ice cream, immediately getting all the children's attention.
In Battle Lines, part 1, Michelangelo is briefly shown training the orphans in basic unarmed martial arts, with Jennika and Casey's help.
In issue #89, the orphans have their first Christmas at Foot HQ. After a night of soul-searching in which Splinter is supernaturally visited by the ghost of his clan brother Oroku Saki and three members of the Pantheon, he decides to take his own role as a father and caretaker more seriously. Using Foot Ninja to forcibly summon the Turtles and their closest friends to HQ, he surprises them all with a Christmas party for their family and the orphans, with himself dressed as Santa Claus for the occasion. Alopex, Angel Bridge, Woody Dirkins, Jennika and Casey Jones are shown to have come.
- The apparent ages of the oldest children have changed significantly since their introduction. In Kingdom of Rats, few or none of the orphans appeared to be teenagers. But by their next published appearance in issue #85, at least a few of the orphans are clearly teenagers of high school age.