From the study on twins, I assume that yes this thing could also affect siblings. Although it doesn’t have to be… I think? For example, it could be that one gets F from the mother, and then Ji from the father. Or maybe it’s something more hormonal and happening in the womb rather than genetic? So epigenetic? I have to say that many of our characteristics are some mix of genetics and upbringing, so I tend to want to believe that personally.