Could this be as simple as "internal" family fighting? This is just one theory, thoughts or my opinion.
Let's say that the kids in this family fought for their place of importance to their parents. This happens in most families, sibling rivalry, especially in a divorced family (JMO). You have the oldest, who is the one who goes through the learning process of first time parents, later they have more responsibilities than the younger children because they are the oldest. Resentments start here for the oldest. Along comes the second child a girl, who becomes Daddy's little princess. Then along comes the baby, mommy's darling little boy. IMO, the "baby" becomes the most spoiled and gets away with more things than the other children. In this family situation, these things are true. The "older" children feel jealous of the "baby", don't think it's fair and etc, etc. But although the jealous is there, you'd better not touch that baby, because they'll beat the crap out of you for it! They have that right but no one else does!
To me the Rhoden family fits this scene. After Dana and CRsr divorced, she moved away for awhile and took the 2 youngest children with her, leaving FR there with his father. (this is what I've heard or read). Why?
Anyway, I have seen a FB post somewhere, ( I think in the media) between FR, BR, and ChR,(from awhile ago) along the lines of FR being frustrated with his family and how he was being treated at home. Could have been an upset teenager's rant, who knows?
Here's my thinking though: Could there have been a fight that night between the family and some of their so called friends? Could some so called friends/family have "egged" the fight on? Incouraging these family members to do more damage than they had intended to do and for their own reason's for revenge? Could one of the (insider's) be GR? Maybe he didn't like being "taken care of" by CRsr. Maybe he didn't want to quit using,or/and being told what to do and when. Maybe him and whoever was helping deal the drugs thought they were getting short changed for their "work" (especially after seeing someone getting a new home with a lot of money put down on it). IMO. FR could have been in on it. Again he may have gotten jealous over the new home Mommy got and the old one he had to live in. Other things that had happened in the past could have had him already angry and feeling left out. Maybe he didn't like "sharing" everything that in the past was just mostly about him and his Dad. With little jealous birdies whispering in his ear, telling him he had the right to feel this way (for their own reason's) he'd finally had enough and wanted a "show down". Maybe he wanted to get things straight between him and his father once and for all?
Could all the hate, revenge, hurt feelings and greed being felt by the killers that night have caused this "blood bath"? Did some family members have their own reason's for starting this, and the other's have had their own? Could the "plan" the family members that may have been involved in this been only to show the victims they weren't going to take it anymore? While other's in on it, had planned to murder from the get go?
To me, this would explain how they got into the homes, past the dogs, and had the element of surprise on this family. GR or FR could have hidden guns that CRsr had in his homes, they could let in, or invite the others to their homes with no problem. As for some that were supposed to spend the night, they simple could have told them that, that night wasn't a good time to come, because of an emergency "family" meeting. And because this family seemed to keep most of each other informed on what went on in their homes, all the family would know "who" was there. I think some were killed just because they were witnesses.
To me, CRsr was the main target, maybe once they unleashed all that pent-up rage, it got away from them. But I don't think so, they shot Dana in the face, that is very personal! Her and HHG were overkill big time! With CRsr being a big man and a fighter, I can almost understand the overkill, fear. But when it comes to the women and CRjr I just don't, no fear, pure hate was in that.
This is just one of my theories, but it makes the most sense to me. But that's just me.