@usagijen Awww poor bebe :p Bullying is a sign of affection or so says the bullies.

@vre Yes, the birth order theory is still a heavily-debated theory till now. Studies regarding the proving and disproving continue with no conclusive answers still. Though, that has not hampered my fascination for it. I am just merely using it as a means to possibly explain the behavior of the sisters and how it might also explain ours.

As you mentioned, there are too many factors that come to play with regards to a person’s personality.
Thus, my use of the birth order theory here is just to state the prevailing patterns and compare it against the Minami sisters’ personalities.

All for the sake of discussion and for fun

regarding birth-order:

the theory itself is only hypothetical, but it subjects to many factors and the said qualities can be further categorized based on culture and values and genetics and parents, and so on.

Here Haruka, realizing absence of parents, becomes subject to obsessive-compulsive behaviour due to the necessity of taking the role of carer and pseudo-mother for both of her siblings. At least, maybe that’s what the mangaka perceive on being the eldest and no presence of parents

Maybe another crucial factor is a flawed parenting, popularly depicted in many novels (what comes to my mind is Jodi Picoult). Maybe deviations from the known birth-order pattern in characters of people are what people can relate from media to their personal life right now, due to, well, parents and many other circumstances…. but this is another thing.