Romantically not yet , he does love him brotherly even if he's a little confused.

Lillian , is a moniker that luvian was being called by when he was little , (lily) the flower , In French it's also said Lilian.

(A moniker is a nickname or pet name for a person.)

It has been thought of , but that wasn't the main reason :)

Yes , Arthur was his childhood crush.

Yes , he's still traumatized.

Yes.

Arthur has the ability to erase memories, however if I may say , Arthur's abilities don't work the best on luv.

The cause is still unknown.

there are countless reasons for people to fall in love , and for the blood related part it's how incest works.

There's going to be male leads.