Disclaimer:
I do not own the character, this scene is a transcription of the scene shown in the tv show, which I do not own, too.
"Sometimes [Petyr] sees Sansa and she's the daughter he never had. The daughter he might have had with Cat if he and Cat had been married, as he dreamed when he was a small boy living in her father's castle and was so madly in love with her. But at other times, he detaches himself from that and he's less Petyr and he's more Littlefinger. And she's just another piece in the game of thrones, she's just another valuable piece he's going to use to get what he wants. And yet at other times she's not Catelyn's daughter, she's like young Cat. She's his teenage fantasy returned again. Then his feelings for her are sexual and romantic."
- George R. R. Martin on Littlefinger's feelings for Sansa and Catelyn -
"In a better world, one where love can overcome strength and duty, you might've been my child. But we don't live in that world," lowering his sea blue eyes, his fingers softly picked up a strand of long, ginger hair.
"You're more beautiful than she ever was," his voice had grown husky and the words hung in the cold winter air like tiny clouds. Sansa was sure that the cold air wasn't the reason for that husky voice of his, "Lord Bealish.."
"Call me Petyr," his hands felt surprisingly warm on her cheeks that had cooled out from the time she'd spent outside, building her home that the little brat had just destroyed. But her thoughts were interrupted when soft lips touched hers. Sansa was surprised, not extremely, but still surprised. She had always seen him as the man that had fallen for her mother who never wanted his love.
The man's lips felt soft and warm on hers and the tip of his tongue slid tenderly of hers, but Sansa didn't react. Lord Baelish's - Petyr's - lips felt better and more experienced on hers than Joffrey's when he'd kissed her back at King's Landing.
He could feel the girl's warm breath on his cheek. She felt good. So good.. Better than he had ever imagined. Well, he had always imagined what Cat's lips might feel like, but Sansa.. She was someone so different and during other moments so incredibly much like her mother. Littlefinger was disappointed, he had perhaps told the little dove too much. Out of a bunch of emotions that had overcome him when he saw her there, building Winterfell. The little dove, was she really as innocent as a dove? Could a girl from the north even be a dove?
The pulled away from each other, mesmerized, looking at the other one in silent wonder and awe.
Both with a thousand questions in their minds.