(Inspired by this comment by @b-quieter )
When she’s like, 6 or 7 years old, Hayun thinks that anything Rumi has, she should have, because they’re sisters. She learned this from watching Aeri, Jihae, and Hani share with each other. Usually this means things like food and toys, but there is a brief period of time where she thinks that includes something else, too.
Now, to Hayun, Mira and Zoey are the cool, pretty girls who are always with Rumi, and that Rumi kisses sometimes (and that her nieces and nephew call their moms, too). So, logically (in Hayun’s child brain, at least), because Hayun is Rumi’s sister, SHE should get to kiss Mira and Zoey, too. Every time Rumi kisses her wives, she rushes over to them and demands a kiss, too. No matter how many times Celine and Poppy try to explain that that’s not how that works, and that A) she should be asking, not demanding, kisses from people, B) not trying to kiss her sister’s wives, and C) not trying to kiss someone as old as Mira and Zoey are compared to her because all of that is inappropriate, Hayun won’t listen.
Mira and Zoey, for their part, just laugh it off at first, but whenever they do, it just makes Hayun pout and insist even more that she should get a kiss from them if Rumi does, which annoys the fuck out of Rumi. Things reach a boiling point where, at one point, Rumi tells Hayun that Mira and Zoey are HER wives, so she shouldn’t be trying to kiss them, and Hayun responds by telling her that if RUMI gets to have Mira and Zoey as wives, then so should SHE. This leads to the two of them getting into an actual fight, during which Rumi has to stop herself several times from telling her 6 year old sister that she “already stole [her] moms, she can’t have [her] wives, too.”
After witnessing whatever THAT was, Mira and Zoey decide that it’s time to firmly tell the 6 year old “no”.
Mira and Zoey sit Hayun down and explain to her that she can’t keep demanding that they kiss her just because Rumi gets to, because kissing isn’t like food or toys, and you don’t just deserve to kiss someone because your sibling kisses them. That when they got married to Rumi, they made a promise to her that they’d only kiss her (and each other), and going back on promises is wrong. That you can’t just demand someone kiss you, because that’s wrong, and people should get to decide what someone else does to them.
(They also tell her that if anyone tries to kiss her without asking, or anyone tries to demand kisses from her, to come to them, or her moms, or Rumi, or the girls, because they’ll beat that person up for Hayun.)
She finally stops demanding kisses from them after that.
But then she sees them give their daughters and son kisses on the forehead, and she very shyly comes up to them and politely asks if they can give her one of those kisses. Mira chuckles and Zoey giggles, but they do end up giving her a little kiss on the forehead as well. She smiles and thanks them, and then runs off.
Meanwhile, behind them, Rumi crosses her arms and pouts. “But where’s MY kiss on the forehead?”
(They call her a brat, but they do give her a kiss, too.)