Someone explain this chapter to me in simple words?

that eren have an evil brother in the enemy ranks and is one of the seven titans, so there are 9 titans that have the power to shapeshift to human again and 3 are with eren (tecnically 2 because the power of the royal family of historia was destroyed with her dad) and it seens that ymir have a very important rol in this story after all
but simply this is divergent ones again

Thank you so much it makes sense now

Once upon time, there is battle between mare people that captured the power of 7 titan and elodia people.
The pacifist king of elodia tired of this 70-80 years of battle.
He just want a place where his descendants living in harmony
So he fleed from battle, build wall, and sleeping peacefully, after wiping out his peoole memory and implant new version of history.
A peacefull history.

Thanks