(Ah. Love. Maedhros can vaguely recall such a feeling - long ago - but it is foreign to him now.)

Your foster-brother? (A child of Elros or...truly fostered from another family?) She has made her choice willingly - like Lúthien and like Elros. You must count the time you have together as a blessing and then bid her adieu when she ventures to the Halls of Mandos.

(He exhales tiredly, sadly.)

Encourage your brother to remain an Elf, Elladan. It is important that you do so if your father must shoulder that grief.