Disclaimer: All recognizable characters and elements from A Song of Ice and Fire belong to George R.R. Martin. No copyright infringement is intended.
When Arya was born, Sansa had asked where she'd come from. Catelyn had told her that her little sister had come from Mother's belly and the two year old had been satisfied.
She'd been four when Bran was born, and mere days before the birth she'd asked Catelyn how the babe had gotten into her belly. Catelyn had been at a loss for words. After a long silence, with Sansa looking at her and waiting for an answer, she'd said that fathers put the babes into mothers' bellies.
"How, Mother?"
"It's a secret, Sansa. Only parents know. You'll find out when you're older."
A few hours later Sansa had come back to her looking worried. "Mother, what if someone puts a babe in my tummy? I don't want a babe in my tummy."
Cat had smiled, but Ned had choked on his tea. "No one's going to put a babe in your tummy, Sansa" he'd declared, "Not until you're much older and married." Catelyn had thought then of her husband's bastard son Jon Snow, wrestling on the floor with Robb mere yards away, but she'd said nothing.
Sansa was eight now and Catelyn knew there weren't many years left until she would need to tell her about the monthly flow of blood that made a girl into a woman and the dangers and temptations men would present then. However, as innocent as Sansa was, the other children in the castle were not, and Cat found herself having to explain sex to Sansa much earlier than she'd anticipated.
"Mother?"
Catelyn opened her eyes to see Sansa standing beside the bed, distress on her usually cheerful face. Cat raised herself to a sitting position and gestured for her daughter to join her on the bed. "What is it?" she asked, expecting to hear a tale about some naughty thing the other children had done.
"Jeyne told me something dreadful, Mother. She said men put their manhoods inside women and that's how babes get made."
Cat was scrambling to think of a more delicate way to explain it, when Sansa continued, "I told her she was wrong, of course, because you and Father would never do that. But then Arya said she was right and that's what the horses and dogs did and that was how they made foals and puppies. I said she was a baby herself and she didn't know anything about it, but she pinched me and said she'd show me. So I went with her and she showed me two dogs playing and made me look between their hind legs, and she was right; the dog had his manhood inside the bitch."
"Yes, Sansa, that is how babes are made," Cat began.
Sansa burst into tears.
Cat cuddled her eldest daughter as close as her big belly would allow. "It's all right, sweetling. Don't cry."
"I don't want to do that, Mother. Not ever."
She knew Sansa was very fond of love stories so Cat tried to sweeten the idea of mating for her. Talk of duty and the possibility of wedding a man she did not yet love could wait until she was older and would understand better. "It's different for people than what you saw the animals doing, especially when a woman and a man are in love. When they're in love, it seems like a wonderful thing to do and they enjoy it very much."
"Why don't they kiss instead?"
Catelyn bit back a smile. "They do kiss, Sansa, but sometimes they want to do other things. When the singers sing of lovers laying down in the grass, that is what they're doing. "
"I suppose it's not so bad if the lovers in the songs do it," Sansa sniffed, wiping away her tears with a handkerchief.
"No, it's not." Catelyn smoothed back her daughter's hair. "Go bring the hairbrush and I'll tell you a story about the first time my father took me to King's Landing."
She knew he would be more appalled than amused, but his fatherly protectiveness amused her, so Catelyn told Ned about it that night as he rubbed her back to ease the discomfort there. "I had to tell her people do it differently than dogs," she said, chuckling. "But I was thinking to myself 'when your belly's big as a castle and that's the only way you can comfortably do it, it looks a lot more appealing.'"
"Sansa's much too young to have to worry about such matters," Ned said. "I'll talk to Vayon about Jeyne, and, Cat, remind Septa Mordane to keep a closer eye on Arya."
"How did it go when you had this talk with Robb?" she asked him, curious.
There was no answer.
Cat glanced over her shoulder. "Ned?" The sheepish look on his face told her everything. He hadn't had the talk with their son yet. "Ned! He's eleven. Who knows what nonsense Theon has already put in his head."
"I'll talk to him and Jon, but there's no need to hurry things. They're only boys."
"Just see that you have that talk before they give the serving girls big bellies," she said dryly.
"They're too young!"
Cat arched an eyebrow. "How old were you the first time your cock got hard?"
Ned considered it for a moment, and then an alarmed expression appeared on his face. "I'll talk to them soon."
"That would be best," Cat said, sitting up and turning to face her husband. She gave him a mischievous smile. "How is your cock now, my love?" she asked, cupping him through his breeches.
"Your back pain..." Ned started to protest, though Cat could feel his interest stirring in her hand.
"It's gone." She spread her thighs. "Your attention is required elsewhere, Lord Eddard."
"I had best do my duty then, my lady," Ned teased her back, gently squeezing her swollen breasts. "Maester Luwin had a raven that needs a reply and Ser Rodrik..."
Cat groaned and kissed him, putting an end to talk for the rest of the night.