I hear that expression a lot in AA meetings: someone (usually a male, but occasionally even a female) member will say, "Back when I took my first hostage," referring to an ex-spouse. People may laugh, but it is the same kind of laughter that accompanies all kinds of horrible admissions--it isn't that it's funny, we laugh because we were such idiots and we don't have to live that way anymore.
Basically, the expression just means that alcoholics tend to bring their loved ones right down into the mess with them. It isn't (usually) that they set out to do it, it's just the way things tend to work. And yes, absent some kind of actual abuse, the "hostages" are often complicit in it because THEY don't know how to detach. Everybody in the family gets sick, all around the alcoholic in the middle of it.
So even though nobody PLANS for it to be that way, and nobody WANTS it to be that way, families tend to wind up feeling trapped and miserable, not unlike a hostage situation.