Ani To Wa Koinaka Nandesu Ga.
Chapters 1-3: step brothers. Chapters 4-5&(extras): author and university student who were friends since middleschool.
Nii-chan, Icchatte!
Chapters 1-2: siblings of a 3rd yr highschool, 2nd yr highschool and step sibling of 3rd yr jr.high but the 2 year gap step siblings are more closer.. Chapter 3: the teasing of student council president who was close with the 3rd yr eldest was unconsciously jealous towards the youngest for the attention from SC pres. Chapter 4: college student, convenience store part-timer former co-worker.
Gokudou Darling
Chapter 1-5: host lost his mother who remarried to a (unknowingly) yakuza leader, now the will left behind was to give the host his part of inheritance and the next leader come to meet him.. Chapter 6: oneshot about cats andromorphism and extra from main story.
Aniki to Isshoja Nemurenai
Chapters 1-2: step siblings so close! Chapter 3: boss & subordinate, business trip surprise & misunderstanding. Chapters 4-5: a menacing looking sensei & the student attach to him. Chapter 6: extra from all chapters.
Bomb Heaven