@_wolfsie_ Nah, you aren't being stupid. Reading this weekly is pretty confusing so, like @Barrier-kiun, I'd recommend re-reading the Shibuya Arc. I feel like this manga would've really benefitted from being released monthly but, being a Shonen Jump, we don't have that luxury.
To address your points specifically, the Blood Manipulation Guy, Choso, received a memory about Yuuji being his "younger brother" (why this happened is unexplained IIRC). On top of that, Noritoshi Kamo, who was revealed to be the identity of the curse inside Getou, was an infamously evil sorcerer who experimented on the Death Painting Wombs (Choso's brothers) and manipulated their birth mother.
As for Megumi being the family head, I believe this took place in the Gojou's past arc, but an agreement was made between Megumi's dad and the head of the Zen'in clan, relinquishing Megumi to the Zen'in clan. I'm pretty sure the exact terms were unclear, but Gojou played a heavy role in preventing Megumi from being instated into the Zen'in clan. This is why, upon his incapacitation, Megumi is to be brought into the clan and become its leader.
Hope that helps a little bit.