From what I gathered so far Yotsuba is a clan that's all about power. The one that held the 'head' tittle is the one who has the biggest power, no matter their state of mind. I remembered someone wrote that Maya (the current head) is somewhat a screw-loose from past traumatic experience, but since she's the strongest after Miya died (did she died or disappeared? someone correct me please) she was hailed 'clan head'. From that alone I think I get the picture of what a 'sick' clan it is.
Oh, can anyone explain the ranking level of Magician? I know the highest is Strategic Class, and then followed by Combat Class?
Saying "the Most powerfull in the House will be the Head" its inaccurate, Yotsuba Main House Blood Line comes far I known:
1) Genzou Yotsuba: Miya/Maya Father.
2) Miya Shiba: eldest twin Daughter, its not clear why she declines being the Head, but someone says was cuz health problems, due magic overuse.
3) Maya Yotsuba: was engage with Koichi Saegusa, was abducted, raped and suffered torture, according Vol 8 She was recently appointed as Head, She aunt of Tats/Miyuki, cousin of Mitsugo and 2nd grade cousin of the Kurobane twins.
4) Tatsuya: eldest Son of Miya and from main line, He was demoted cuz above mentions.
5) Miyuki: only daughter of the main line and remain last option.
6) Genzou sister (dont known her name but her last name should be Kurobane), is MY BELIEVE and far I known is not in the MKnR She was the Head replacement till Maya could assume her position, Miya/Maya was 12 years old when their father died.
6) Mitsugo Kurobane: Son of Genzou sister and Miya/Maya cousin.
7) Ayako Kurobane: daughter of Mitsugo, first born of the twins.
8) Fumiya Kurobane: eldest son of Mitsugo.
Their system are Patriarchal, but male descendant or not, main blood line still have preference in the Heir line, Mayumi have 2 elder brothers and 2 young s sisters, She will become Heir if Her 2 brothers die, that's why Shes a "blue ribbon price" and according their Clans Social system Her role is more like high class asset to her House, same for the twins, in Vol 3 is said Koichi ready received engage offers before She entrance in High School, still, seem to be Koichi have an underhand card move, Juumongi, as first choice endorsed from Clan council decision, offered Her hand to Tats in Vol 4, due Tats avoiding trouble (from His point of view) deflect the propose individual as someone to be engage with the 10th or 5th Clans heirs, there Juumongi thought Tats prefers "younger" and offer the twins (Mayumi imoutos), Tats still playing dummy and as commoner facade says He not have that kind of mind set, Katsuto left Him with a warning and some from my POV: "think about it, We will talk again" (this is not in the LN, but is what I understand), I still think that's wasn't a bluff and even something not match entirely well, as one of the points: Ichijou have imouto, Why they only "offer" Saegusa daughters and not other from 10th Master Clans daughters, like 1st Clan daughter or even Fujibashi from 9th Clan.
There's two different things from Ranking and Classification:
Tatsuya will be C Rank as maximum (Major Kazama is B Rank, Miyuki, Mayumi among few others could easy being rank A or even S), , but is Strategic Class, the world population are like 3 billion persons, from that some like 10% are Magicians and from that an guessing average of 50 are Strategic Class, 13 where known and hold the title as "Apostles", Tats is non declare SC Magician, so he belongs to the guessing 37 or so unknown SC Magicians, after "Scorched Halloween" event Japan cant keep void or hiding their 2nd SC Magician: Tats, they gave him the Military unit cover of 101st Magic Battalion and the alias of Special Lieutenant Ooguro Ryyuga (I hope its correct the name), they trying to playing as USNA do with Sirius, their SC Magician.
BTW: according Maya, now is 12 apostles, thanks Tats doings.