The thing that gets me is that whole community seems a little strange in regards to family interactions....EVERYONE in that town seems to be distantly related somehow (joking, somewhat). If you think about it, you find names intermingled all over...Zipperer is somehow related to Kusche, and I think I read somewhere Remiker too maybe? Heck, even with the Halbach's. Teresa's mom ended up marrying her father's younger brother, for heaven's sake. So the town has no place looking down on the Avery's for something that seems to be common practice in that area, IMO. I think it is that the Avery's owned a junk yard which was also the family compound, coupled with the fact that it was in a prime land area and they refused to sell. I do not think it is coincidence that SA's problems all began in this saga, with a cousin that just happened to be married to a member of that sheriff's office and that the crimes she was accusing him of sounded suspiciously like Allen's crimes instead. IMO, this was a concerted effort, from the beginning in 85, to get the Avery clan discredited so that they would sell that land. The Avery business suffered from then on, and Hermann's competing business flourished. The Avery's also didn't help themselves any in regards to the brothers sexual and violent convictions and allegations either, TBF. SA may have had allegations made against him, but I find it telling that they were unable to secure any CONVICTIONS against him of a sexual nature, though.
As far as it being strange of a brother and sister purchasing those types of items together, I think you also have to look at what the family dynamic is. I have a very open family and could see going to such a store with my brother and his wife and not thinking anything about it. I have actually went with my sister and mother to such a store when I was younger (in my twenties, lol) and purchased items, so this doesn't seem that unusual for me. It just would depend on the family, IMO.