This occurred to me for various reasons, so mostly I'm just interested what people feel on this subject.
For me, while bondage doesn't have to include outright sexual elements (often times I even prefer it doesn't) the thought of tying someone up/being tied up is inherently sexually arousing to me.
That's why I personally couldn't get into stories featuring young children, family members, etc.
How about you, how sexual is bondage and everything related (humiliation, the whole BDSM spectrum) for you?