Card text says if you control a blacking other then this card, you can Special Summon this card from your hand.

It doesn't allow for this to happen. Ive only had Blackwing Kris the Crack of Dawn on field yet no special summoning option appeared for the Harmattan in hand.

Also,even when normal summoned, it doesn't allow for the addition of another face up Blackwing's level to increase its own. The option does not appear either.