Also hoping not but it is making me increasingly uncomfortable seeing them try to mother role ariamel & all the people assuming her and grey must be a thing when she is literally a small girl...
Like 😩 hire a house keeper or something super daddee so that aria can be a kid properly too.
She's just being responsible

It isn't abnormal for older siblings to take on motherly roles. She likely has a puppy crush on Grey, but it is extremely unlikely that Grey will see her as anything other than his responsible daughter. They are just joking around a bit with it, creating misunderstandings which really mess up the hero (for obvious reasons) until the misunderstanding is cleared.
Also, remember those drawings from chapter 5.2? The ones the kids drew? Those were actually drawn by the author's own 3-5 year old children

He is just a dad who is making a story that is inspired by his own kids. Hence why he was able to describe the "Grey slipping out of bed without waking his kids" scene so well XD