Think "bonnie and clyde" when you think of Mr and Mrs Gobbo McGoblin.
The family that slays together, stays together.
Rather than a single dominant parter, I see goblin marriages to be more open ended partnerships, with pleasure taken in shared murder, and in producing offspring more diabolical than themselves.
I would see "sex for pleasure" being only with that life partner, where "sex for torture", such as rape, would be accepted by both spouses, and a thing bragged about, but any offspring from such a union being considered "meat", having been sired on a lesser race. I see goblins as experiencing a major headrush from murder and dark plots going well, on par with being orgasmic. As such, I see them as being like BDS&M types, with very VERY different social moes from other races.
I can easily see a goblin "couple" whipping the dogshit out of their "new house slave", then retiring to the bedroom.
I see goblin peer-heirarchy established by example, with individual goblins within the society either establishing themselves and a personal history to prove self worth to the collective civ, or being killed to be made an example of. Within that heirarchy, there is "mutual respect", and a "code of conduct", with the penalty for infraction being death in most instances.
Eg, the goblins each have a home they police themselves, within which they expect to be treated like god himself. Tressassers, or those who slander in another's house are killed outright, and made an example of as a "personal matter". Likewise, rivalries between peers are setted with secret violence, again, a "personal matter."
This destructive behavior is held in check by limited collectivism, such as dynamic duo husband/wife teams, or even family reprisals. Choosing to off a rival means choosing to also off all that rival's supporters. A potential road to great respect in the civ, but also a very big gamble. I would expect that attempting it and failing by being killed instead, would be viewed within the civ as a sign of weakness in that group of supporters and family, and thus be internally advised against, except where "absolutely sure" of success.