Returns the other children of each cell's parent.
Details
The parent is the one get_parent returns, the coarser cell
holding the cell's centre, and the siblings are its children as
get_children returns them: the siblingOf relation of
OGC Topic 21 with inheritID true.
Examples
g <- hex_grid(resolution = 4, aperture = 7)
cell <- lonlat_to_cell(16.37, 48.21, g)
get_siblings(cell, g)