updated Tobirama's family tree to reflect the addition of Hanako to the world.
Hanako is illegitimate, her two siblings are legitimate - she was a recognized member of the senju clan but some records were conveniently lost and by the time they were going to fix it she was legally an adult in the eyes of shinobi law and refused to sign them because some people thought she should settle down and get married and she was not about to do that. So she refused.
Tobirama's relationship with Chizuru is a 50/50 shot if people think its okay, while comon in the times for multiple partners/wives/husbands his brother is the hokage so he should have more respect or something. Hashirama is just happy his brother is happy -yall leave that man alone.
Chizuru was picked by Kaede to be Tobirama's second/other wife because she couldn't have anymore children and knew they'd need to do something because of clan pressure at the time to rebuild the senju line after the warring states era. (which happens to some extent in this AU-but im not sold on how much yet)
Itachi is two years older than Hanako, he might have helped her lose some paperwork. She's happier when not chained to clan bs and he likes for his siblings to be happy.
Hanako thanks her brother by helping his marry Chiharu, since she's not a shinobi and not from Konoha.
Itachi and Hanako cause more trouble for Tobirama than he will ever admit too, he loves his oldest two kids dearly but they really know how to get under his skin and cause him grief. Especially Itachi who is usually very stoic but Hanako brings out the mischief in him like no ones business.
There is a bit of a gap between Tobirama's older two kids and his younger two kids.
Hanako at some point sleeps with a diplomat from Uzu and has a daughter, who is a year older than Itachi's son. This diplomat is also Kushina's father.
Yawen and Ichirou do not get along. However Yawen loves Ichirou's wife and they are great friends. Ichirou is just too much like his grandfather and his sense was Shimura Danzo so he's... a complicated guy. Ichirou gets along with so very few people.
Yawen and Orochimaru hook up and have a daughter, Orohime, who looks like her great-grandmother for the most part. Orohime is six months older than Hatake Kakashi. She is very close with her great-grandfather and great-grandmothers.
Miho is in the naruto parent gen, and its likely that Arai is technically at the beginning of the sannin's gen or at the tail end of the first student gen(Hiruzen and co)