I see the example sibling relation between two different model, but how to do it with the same table ?
Something like a table that contains all nations and a pivot table that contains two columns: nationParentId and nationChildId whitch point on the same table ?
Can you explain how to implement ?
It should be exactly the same. The pivot can hold a reference to the the two users pointing to the same table without an issue. Just make sure the column names and properties are different