I'm curious about the fact the realtor wanted them to sell so badly to a family with children, seeing as how big the house is for just two people (in her opinion), then after they die, she sells to a couple with one teenage daughter likely to leave the nest soon, leaving behind the two parents. Made no sense.
Well, it wasn't just any realtor. Jane was Barbara's sister. I got the impression that Adam either inherited the house from his family, or bought the house when they were both young and they expected to have a lot of children, but Barbara found out she couldn't conceive or something (explaining why she gets a bit upset at Jane for mentioning a family with children, as if Barbara and Adam aren't good enough or something).
To me, Jane felt like she wanted a lot more out of life and just assumed that her sister wanted the same things. Barbara just wanted her simple life with Adam, whereas Jane wanted money bigger things (she emphasizes that she showed the photos to a couple from a big city, tries to advertise herself as a house decorator to the Deetz family, etc.)
I always assumed that was the case, as opposed to being cousins, on the (not necessarily true) belief that siblings would be more direct with each other, to the point of tactlessness. Also, the relationship reminded me a lot of the family dynamic of some friends.
I realized tonight that the Deetz's are the couple Jane (the realtor) was talking about! She mentions that they offered $260 mil from just a picture. That same day, the Maitland's die, and when Jane drives away from the house after they died (she and her daughter were in black, like they'd just come from the funeral), the house had a for sale/SOLD sign on it. It had to be the Deetz's!