Verse 3:

When I was a boy in my father’s house,
still tender, and an only child of my mother

This is an interesting bit of narrative. Solomon was the son of Bathsheba. The woman with whom David committed adultery.  He subsequently murdered her husband, and tried to cover it all up. But God knew better. But this seems to indicate that (at least for a while) Solomon was an only child. I wonder if he was always an only child, or if Bathsheba and David subsequently had other children who are not mentioned. Interesting…