In eccentric binary systems, circum-binary discs that are sufficiently inclined to the binary orbital plane align in a perpendicular configuration (called polar configuration) with respect to the binary plane. In hierarchical systems with more than two stars, polar alignment is studied with pure binary criteria. Recently, we showed analytically and numerically, via SPH simulations with PHANTOM, that pure binary criteria for polar alignment are necessary but not sufficient for polar alignment in hierarchical systems. In this talk, I will present the generalized criteria and I will compare the observed distribution of disc inclinations in the binary and in the hierarchical system populations. I will show that how disc inclinations are distributed in stellar populations strongly depends on the multiplicity of the systems and thus, better understanding alignment conditions in hierarchical systems is critical in order to well interpret these data.