Han:
You neck. He loves it when you give out small, soft moans. He also finds this hilarious, as he bursts out in laughter when doing so.
Leia:
Your cheeks or nose. She loves to see you scrunch up your face when she kisses your nose, and she finds kissing your cheek cute.
Luke:
Your lips. He feels that they are delicate and fragile, as he is always gentle when he kisses you. He loves to feel your soft, warm lips.
