A/N: This fic contains consensual, non-sexual age play. If that's not your thing, don't read further.
"Baby, Auntie Kara will be here any minute. Are you sure you want to wear this?" This was an absolutely adorable Supergirl pajama set, complete with red, flapping cape and a hood that looked like Kara's flowing, golden locks.
Green eyes stared at Alex uncertainly. "Yes." Lena nodded as if to deny the way her voice had wavered.
Alex crossed her arms. Lena had mentioned bringing Kara in on the new dynamic in their relationship, but was this really the right time? Lena only got like this when she'd had a rough week at the office. And Alex hadn't thought to prep Kara for any big announcements at their weekly Movie Night. "Lee?" she asked, waiting to see who would answer.
"Pwomised no more secwets, Momma." Lena's voice was tiny, but her eyes seemed huge as they glimmered with big, fat tears.
Fuck, Lena was going to rip her heart out. Picking her Little girl up, Alex brushed kisses all over her cheeks. "No more secrets," she echoed. It had been the first thing Kara and Lena had agreed on when they began to rebuild their friendship. "We'll tell Auntie Kara when she gets here." And Rao help Kara if she said something to hurt Alex's baby. "Why don't you pick a movie, and I'll order dinner."
Lena considered that, arms wrapped tightly around Alex's neck. "Potstickewz?"
"No," Alex said firmly. She observed Lena closely. Teeth gnawed a trembling lower lip. Terror stilled the usual frenetic energy of her Little for a long minute; a minute where Alex glimpsed the Big version of her girlfriend warring in the depths of Little Lena's expressive eyes. "Lee?" she asked again.
"They're Kara's favorite." Big words in a Little mouth.
"Yep, and we aren't using them as a bribe, Lee." Alex addressed her girlfriend. "I understand you want to keep your promise. I know it's important. But Kara's an adult. So are you, sometimes." She tried to lighten the atmosphere with that last - and a smacking kiss to Lena's forehead.
Lena's answering sigh came all the way from her toes. "Don't wan' her to be mad, Momma."
"Auntie Kara loves you, baby. Remember?" So much that Alex had hesitated to approach Lena, not wanting to encroach. "You're her very, very bestest friend. She likes you even more than Momma."
That earned a real smile from Lena. "Is OK Momma. We bof luv you."
"I'm glad, baby. Momma would be really sad if she didn't have your love." She danced them around the living room for a minute until Kara knocked on the door. "Want to answer, baby? Or should Momma do it?"
The body in her arms resembled a statue. "You," Lena whispered.
Hiding her own unease, Alex set Lena down before striding to the door. "Hey!"
Kara grinned and held out a bottle of wine. "Lena mentioned you liked this one, so I picked it up on the way over." She gently shoved her way past Alex after handing off her gift. Her laugh filled the apartment. "It looks like I've got another copy of me. Are you going to help save National City?" she asked before wrapping Lena in her usual hug.
"Kara..." Alex put the wine bottle on an end table.
She wasn't fast enough. Kara stepped back immediately. "Did I hurt you? Lena?" Her voice thinned with panic, and Alex put a hand on Kara's shoulder. Her reassurance fell flat. "I'm sorry!"
Lena was crying. The tears from earlier were insignificant in comparison to the ones rolling rapidly down her cheeks. "Auntie Kawa." Her childish pronunciation dropped a few more years, and she held out her arms to Kara. "Dint hurt me. Wants more hugs!"
Alex, hand dropping to her side, hovered between her sister and her Little girl. Please, she silently begged Kara, please don't hurt Lena even as she wanted to engulf Kara in a supportive embrace. Losing control of her strength always sent her sister into a spiral of self-doubt.
"Lena?" Dropping to a knee, Kara stared at Lena in clear confusion. Her eyes bounced between Lena's tear-streaked face to the Supergirl pajama outfit. Her arms slowly rose. "Come here, kal. You're always safe with me."
Moving so fast that her Supergirl "hair" fell off her head, Lena dove into Kara's arms. "No more secwets!"
Unsurprisingly, Alex spotted tears on Kara's cheeks. She wrapped her arms around her sister and her Little girl. "No secrets in this house, baby. You kept your promise to Auntie Kara, and Momma's so proud of you."
Alex was investing in earplugs. Maybe she could use some of the alien tech at the DEO to design something completely soundproof. Anything to stop the off-key (Lena did many things well. Singing was not one of them.) duet ringing through the living room.
"Do you want to build a snow man?" Lena bellowed.
Emanating sunshine and happiness from her pores, Kara whirled her niece around the room. "Come on. Let's go and play!" They sang together before Kara took the lead.
She missed the days when Big Lena had threatened to throw the Frozen DVD from her L-Corp balcony. Still, the dancing and singing duo made a pretty picture. Fishing her phone out, Alex snapped a shot of them amid an ungainly ballroom twirl, mouths open and cheeks pressed together.
Bleeding ears be damned. Staring at the photo, Alex smiled. Her life was perfect.
Translations:
kal = a child below the age of 15 (approximate Earth years) who is able to speak clearly