I don't really understand the whole part with the doctor's "boyfriend". Was he really Nook's brother who got a sex change, making him her sister? Did the doctor not know they were the same two people? Or are they two separate people? If so, when did the "boyfriend" die? I must have missed that... Did the ghost's merge?
... I'm awfully confused. Can anyone help?
Yep, it was Nook's brother who presumably fell in love with the doc and had surgery to change his sex so he could marry him. The doc was fully aware of the sex change. When the pregnant sister "gives birth", I guess the ghost was reborn and was now what she was before; a dude. I'm too tired to figure out any symbolism, but it probably signifies something.
With the nurses outta the way, he has the doc all to himself.