You'll no doubt find through the
search feature that this topic has been well covered, but generally it can vary from campus to campus. I can't speak for other GLOs, but for SAE at least it's still ultimately up to the chapter in question whether or not to extend a bid. Being a legacy will generally guarantee that the chapter at least considers you, out of respect for the alumnus/alumni to whom you're related, but that's as far as any guarantee goes. You have to earn a bid on your own merits.
ETA: What OTW said.