in Louisiana:
delta/omega/kappa/alpha
i've neve seen a delta and a sigma relationship.
aka/alpha/omega
i've also never seen an aka/kappa married coupled.
zeta/sigma and sgrho/kappa/sigma
****************sidebar

ersonally, i try to steer clear of greek on greek relationships... you never get any privacy in your relationship here. too much in the public eye. it's convenient sometimes, but mostly a pain in the butt.