This is a great subject. The idea and extensiveness of the concept of "ownership" and the moral vs practical uses and applications thereof.
If we boil the idea of ownership down to a basic concept... Let's consider a bar of chocolate. I brought it and laid it on the table between us. I brought it there, it is mine. Let us not consider how I obtained it.
Let's just say I brought it there and now it is between us, at an equal distance. Whose chocolate is it?
What if you take it? If I object this action the subject of ownership will come up and the strife will begin and will be settled by might or brains. If I said nothing however then it becomes your property because I did nothing to stop the chocolate from transferring ownership.
In that example I decided to give up and let the chocolate go.
Thus ownership can also be thought of as the condition of how hard I will work to keep mastery or possession of something.
Nothing really belongs to anyone. Not even ourselves if we are unwilling to look after ourselves and fight to keep ourselves alive.
Interesting example, but if you don't say it's yours, someone can assume it's a gift left by someone. It doesn't require fighting, but speaking. The other who doesn't want to be moral will be the one who instigates violence in a physical manner, and that's why there is work to fight for what's ours because others don't care and just want to take even when it's not theirs.
But we do belong to ourselves. How we treat ourselves in another issue apart form self-ownership.