Initially at Every St, when there were ructions in the marriage, Margaret chose to sleep in the caravan, but after a time she swapped places with Robin. This may have coincided with when Robin got the job of principal at Taieri Mouth School and was no longer resident at Every St during the week, so it made sense for Margaret to use the bedroom and Robin to use the caravan, to sleep in.
Joe Karam argues that because Robin slept in the caravan then he qualifies as being "evicted from the house". This is far from true. From what we know, Robin carried out all household activities within the house, including, as is very clear from the evidence, using the house to pray in. Hundreds, maybe thousands of people around the countryside provide extra accommodation in a similar way for their families by parking up a caravan or turning a garage into a basic sleepout.
Further to this when the Taieri school house became available, Robin continued to stay in his old Commer van during the week, passing up perfectly good state funded accommodation in so doing. We can only speculate on his reasons for doing this. Maybe he wanted to leave as small a footprint as possible on the planet, or maybe he wanted to avoid the likelihood of the house becoming a burden on his simple routine, or maybe he just liked the sound of birds in the morning, we will never know. All we do know is that it was Robin's habit to prefer living in temporary accommodation.
Finally, it is quite common for a couple of Robin and Margaret's age to sleep in separate beds. If Robin had not been so partial to temporary accommodation then maybe the family might have made one of the two living rooms available for him, but that is not what happened.
There is no clear evidence as to what the state of Robin and Margaret's marriage was although there are many stories of how Margaret referred to Robin as 'Belial' (or Satan) and this is taken as clear evidence of dischord. On the one hand they had plans drawn up for a house they were building together while on the other there was talk of Margaret moving out into a separate dwelling with Stephen, but that may have just been a plan for a temporary arrangement once the house was pulled down and before the new one could be built. In our very liberal age we forget that not long ago a couple were encouraged to stay together through thick and thin, and even while mouthing off at each other, the bond that holds a couple together is ultimately stronger than the words that threaten to pull them apart. In his sincere Christian belief, Robin may well have been of that ilk.
Given the state of Margaret's strange beliefs, her sedentary lifestyle and her material dependence on Robin, Robin's situation could be compared to that of someone living with someone with a difficult psychological disorder. Anyone who has watched their loved one slowly being taken over by a degenerative psychological condition can find it both stressful and conflicting. The desire to leave the family home in response to Margaret's rejection of him would have been counter-balanced by his desire to remain with his children and the knowledge that Margaret had no means of providing for them. It is also possible that Margaret's attitude towards him went in cycles, a behaviour common in many psychological conditions, and that she spent as much time being caring and loving towards him as she did reviling him. As with caregivers of sufferers of any condition where sufferers display annoying and inappropriate behaviour, Margaret's taunts may have had a meaning to Robin, in respect of his relationship to her, that was quite different to that interpreted by other observers.
Ultimately the state of Robin's relationship with his wife and his family is likely to have been complex and multi-layered and no simple conclusions should be drawn.
No family in our society is completely free of dysfunction. Most families have at least one family member for whom some psychological dysfunction represents a challenge that requires extra effort to overcome, whether it is something as simple as dyslexia or something more complex such as anorexia or depression. In many respects, the Bain family was very functional, they were close knit and lived together as a unit with a father who was always able to provide for them materially. The eldest daughter was head of school and was studying to be a teacher like her father. It is very easy, on the basis of the condition of the house they lived in and the very tragic way in which the family met their demise, to label them as the most dysfunctional family in NZ, but the truth is that they were probably only about average. Robin, Arawa and Stephen were probably above average functionality. Meanwhile Margaret, David and Laniet were probably less than average functionality. In my biological family there was at least as much dysfunction as there was in the Bain family, it's just that we lived in a tidy house. Certainly none of my siblings was ever a contender for head of school.
Update: In David Bain's interview with Justice Binnie he confirms that Robin was indeed very much part of the household. From the interview, page 46 (Q refers to Binnie, A to David):
Q. Now when you spoke to the police, you said you went in search of your father and the question is why you'd look for your father in the lounge?
A. Ah, again I can only give you what I made in my, in the statements and, and in evidence and so on and that was really his influence, he was most concentrated, he spent a lot of time in that room either working on the computer or praying or, you know, discussing things with visitors that he might have had.
Q . Well, I think it's this idea that, that it's the room where he had exerted the most influence?
Q. I understand from that but because he was living in this van, that that was the room within the house that he did whatever he had to do.
Q. Is that what -
A. Yes that's correct.
Q. It's an odd way of putting it, this is a room where his influence was focused -
A. Oh he was just -
Q. Can we kind of get at what you mean by that?
A. Well, it was the room where he could be away from Mum and still, I guess go about his business that he would do and in the household without her being overbearing or beating him down and telling him off or, you know, the various things that she -
Q. It's a bit of a sanctuary?
A. Well, for him it was. And it was, it was deemed that for, for all of us as well that if we were to have, um - 'cos we, we kept that room cleaner and tidier and - all the rest, than the rest of the house in order that if we did have, you know, visitors that was when have the, you know, a cup of coffee with them and you know, chat with them . Formal, a formal room so to speak.
Q . Rather than the living room where the television was located?
A. Yes, yeah.