My mother is a Pi Phi with a relatively negative experience, though she never disaffiliated. My father was not AT ALL interested in Greeks. When I told my mother I was going through NPC rush, she had her reservations but started to get excited when she realized I would be in HER chapter house. Both parents were supportive when I decided none of the sororities was for me.
My parents didn't so much know about my joining Theta Nu Xi until after the fact (they knew I was interested in a sorority but didn't have details.) After I joined, they were both hesitant, but I've shown them how much I love my Sorors, so they're both quite supportive. My mother even purchased my first jacket as a crossing gift.