Some TMNT stuff really isn't for little kids.
Scul and Bean are both more independent and intelligent then other Malignoids who are slaves to Maligna's telepathic control, presumably due to their general status. They have separate bodies but can communicate telepathically. Their bodies are covered in an armored caprice making them resistant to most attacks, though extremely strong warriors can damage them. Bean has the ability to fire toxic bombs from a hole in his head which can incapacitated his foes. However if the hole is blocked, Bean's bomb will explode on him.
Unusually for Malignoids, the two are shown to emotionally care about each other as shown by Scul going back to retrieve Bean and telling his brother he won't let him die.
When Maligna set her sights on Earth, Scul and Bean were sent as the advance scouts for the invasion, with the help of Kid Terra who was working for Mr. Null the "brothers" actually succeeded to defeat the turtles and capture them along with Splinter, April and Mondo Gecko, with the exception of Raphael who escaped. Shortly thereafter an invading force of Malignoid larvae were sent to Earth in asteroids, the larvae devoured everything in their path but the invasion was ultimately stopped by the newly formed Mutanimals, Raphael, and Kid Terra who had realized the error of his ways. Bean scampering away with his wounded brother.
During this confrontation, Slash destroyed the engine of Maligna's organic spaceship. As April and the Turtles escaped, Slash battled Maligna, Scul and Bean, the Malignoid brothers sustaining heavy damage. Regardless of whether or not Slash killed them in combat, not much later, the entire Malignoid hive and Maligna herself were also killed at the end of this story when their Hive-Ship crashed into the sun.