Tell Sarah that she looks adorable.

"You look adorable." You say, smiling at Sarah.

Sarah smiles and joins you on the sofa.

"I guess Sarah won't be having coffee." Brad says, taking her mug away. "I'll go make her a bottle."

Sarah makes a show of pouting about this but doesn't seem genuinely displeased about it.

"How long have you two been..." You're not quite sure how to ask the question. "doing this?"

"Since college." Tanya answers. "I blackmailed Sarah into wearing diapers."

You almost spit your coffee out. "But you're so protective of her."

"I wasn't at first." Tanya admits as Brad returns with a large baby bottle full of warm milk. "I wanted to embarrass her."

"She was jealous because I'm smarter than her." Sarah chimes in as she takes the bottle from Brad.

"Drink your bottle." Tanya tells her playfully. "Children should be seen and not heard."

Sarah sticks her tongue out at Tanya but begins drinking her milk. She lays down with her head on your lap, smiling around the nipple of the bottle as she sucked on it.

"It started out cruel but as I kept treating her more like a baby I got lost in the role and it become genuinely motherly." Tanya explained. "Eventually we admitted to each other that we liked it and we saw no reason to stop."

Then you realise something. "If this is how she wants to live, why is she going out with me?" You ask. "Where do I fit into this?"

"Brad and I are pretty serious." Tanya explains. "We are making arrangements to move in together."

"So you want me to play daddy for Sarah?" Looking down at her it doesn't seem like it would be such a bad thing.

"No. You are not taking my baby girl. She is moving in with us." Tanya shakes her head. "But with Brad always around I'm worried that she'll get jealous."

"I still don't understand." You say.

"You'd move in too." Tanya explains. "As my baby boy. So Sarah has a playmate."

That leaves you speechless for a moment. You look down at Sarah. You don't want to lose her but are you really willing to live in diapers to keep her?