The official "canon" or "word from god" or whatever you want to call it is in the novels. The fanmade PVs you see for the songs (such as where Len kills Miku and MEIKO is made a random peasent who Rin abuses) were created because the novels were not out yet and the official PV videos were too simplistic and didn't tell the whole story (Servant of Evil was the song that made Mothy truly popular and kicked off Evillious for him).
The novels state that Allen (Len) was in love with Michaela (Miku) and that Kyle (KAITO) also fell in love with her. Michaela did not love either of them but loved Clarith (Haku) and always looked out for her. Kyle's love leads to the events of Daughter of Evil when he withdraws his engagement with Riliane (Rin) and Allen ends up having to choose between his sister's orders and the one he loves.
I recommend reading the novels. You can find the first two on tumblr. Cloture of Yellow is the first.
so u didn't watch dauter of green yet, right ?
There is no Daughter of Green. There's a Daughter of White, and a Wiegenlied of Green. But no Daughter of Green.
Not to mention this person's question was answered months ago.