My honey-dew is a GDI and we at times bumb heads. During my process I was not home much and I think he miss understood the entire concept of Greek life. However after I had to check him a few times

, he has accepted that its part of my life and supports me and our events

.
I think Greeks pair up with other Greeks because it makes things a little easier. Your partner would be more likely to understand your passion and zeal toward your organization is they are also actively involved in theirs. For example, I have only ever dated West Indian men (I went out on a date with an African American once). Not that there is any thing wrong with non-West Indian but it's more comfortable, I can really kick back and be me. I believe the same thing applies to Greeks. I think it would be easier if my honey were Greek but what can you do.
I have only ever seen the very stereotypical pair up, Delta/Omega, AKA/Alphaa, Zeta/Sigma.