Yea I think that's why Kuki babies him, at least based on the videos I've seen and mate I've scrolled heaps lately lol.
If there are older sisters in particular (the expectation is on girls rather than boys) to look after the younger sibs, and they often would not even have their own rooms sibs of different genders and ages would sleep in the same bed. Not saying Sedat and Kuki did, but in some cultures this was quite common back 30-40 years ago as families often did not have the resources they may have now.
If you watch a clip where Kuki posts her apartment in Turkey she shows the couches she and one of the girls sleep on, it's basically a living room, thats just quite common and it's common to have heaps of people sleeping in the same space when families visit.
In some cultures this is quite normal, in others it's seen as weird. In Turkey sitting on the floor and eating is acceptable as well as it is in many cultures, my own as well, whereas in the country I live in it's deemed as the most ridiculous thing in the world. Even I think of it as ridiculous, but it's something thats just acceptable and normal in lots of places.