Knitting (BakuDeku)

In this story Kirishima and Deku are step brothers. They share a father and have different mothers.PSA both mothers are not there for them. Kirishima's mother is dead and Inko disowned Izuku. This is also an omegaverse. Katsuki- Alpha, Kirishima- Alpha, and Izuku is an Omega. When Izuku was first presented as an omega big brother Kirishima vowed to keep his little Izu safe from everything that could hurt him. Little did he know that also meant their father. From the age of 6 to the age of 10 Izuku was sexually abused, verbally abused, and physically abused by their father.
One day after Kirishima and his best friend from kindergarten Katsuki got back early from little league practice they walk in on Izuku being hurt sexually by his father. Kirishima loses all control attacking his and Izuku's father with a baseball bat and Katsuki goes over to confront the distraught omega. After some time and a long court hearing their father was sentenced to life in prison and Izuku was given to the care of a mental institute for trauma and healing. Kirishima was angry that Izuku was taken but understood why. Katsuki is more upset seeing his fated mate get taken.
Katsuki had known that he was fated to Kirishima's little brother ever since they saved him from his father. When they touched they both felt the connection that only fated mates get. But he wouldn't dear say anything to Kirishima or try anything with Izuku while everything was happening.
Soon high school rolls around and Izuku is a freshman but as for the others, both Kirishima and Katsuki are sophomores. It was also the year Izuku was being released from the institute. However, before he could somethings had to be taken care of and Kirishima and Katsuki had to talk to the nurses that had been taking care of Izuku.
Also note the bakusquad are all softmores including Todoroki
the Dekusqaud are all freshmen