We had 2 adults and an 8 yr old in a balcony cabin. We did it but it was tight. The Sky's cabins are on the small side and the storage isn't good.
We kept bags under the beds to use as drawer space. There is definitely not enough drawer or closet space.
That said, you can do it. Just be prepared.
Would we sail again on the Sky in spite of the tightness? Yes.
Be flexable and enjoy.