With a hostile expression his father clenched his fist, as if to drive Gregor back into his room […] (1.25)
Mr. Samsa hardly comes out a sympathetic character here. His reaction to Gregor's condition is hostility, rather than patience or empathy.
No plea of Gregor's helped, no plea was even understood; however humbly he might turn his head, his father merely stamped his feet more forcefully […] he drove Gregor on, as if there were no obstacle […] his father gave him a hard shove, which was truly his salvation, and bleeding profusely, he flew far into his room. (1.30)
Again, Mr. Samsa's behavior toward Gregor is brutal. Instead of trying to understand Gregor, he's more intent on punishing Gregor.
[O]ften he heard them say how much they appreciated his sister's work, whereas until now they had frequently been annoyed with her because she had struck them as being a little useless. (2.19)
All is not an utter catastrophe now that Gregor is unable to work (see Quote # 3 above). With her new responsibilities, Grete has a new sense of self-sufficiency and independence that her parents appreciate. Gregor's dismal projection about his family's life without him is proven false; in fact, it hints that his evaluation of his importance to the family is overblown.
[H]is father had put the worst interpretation on Grete's all-too-brief announcement and assumed that Gregor was guilty of some outrage […] [H]is father considered only the strictest treatment called for in dealing with him. (2.27-8)
Gregor can't catch a break from his dad. As in Quotes #1 and 2, Mr. Samsa continues to be portrayed as an unfeeling, domineering authority figure who wields punishment before guilt is established.
[H]e felt very proud that he had been able to provide such a life in so nice an apartment for his parents and his sister. But what now if all the peace, the comfort, the contentment were to come to a horrible end? (2.3)
In this passage, Gregor contemplates life as it was before his transformation when he was the sole breadwinner for the family. Now that he's a bug, the other members of the family lose both the financial and emotional security associated with his earnings.
His mother, incidentally, began relatively soon to want to visit Gregor, but his father and his sister at first held her back with reasonable arguments to which Gregor listened very attentively and of which he whole-heartedly approved. But later she had to be restrained by force […] and cried out, "Let me go to Gregor, he is my unfortunate boy! Don't you understand that I have to go to him?" (2.19)
In contrast to Mr. Samsa, Mrs. Samsa seems to maintain her love for Gregor. She even defends Gregor when she thinks that Mr. Samsa is about to kill him (see Quote #8 under "Morality and Ethics"). But despite her maternal feelings, Mrs. Samsa is still unable to stomach the sight of Gregor.
"It will be the death of you two, I can see it coming." (3.20)
Grete continues to insist that Gregor is no longer part of the family. In fact, according to her, Gregor is contributing to the disintegration of the family and must be eliminated.
"I won't pronounce the name of my brother in front of this monster, and so all I say is: we have to try to get rid of it. We've done everything humanly possible to take care of it and to put up with it" (3.17)
By the time we get to this quote, the apple in Gregor's back is now covered with all kinds of trash (see Quote #7 above). Maybe Grete can forget her family duty so easily here because she can't see the apple anymore? In any case, she refuses to acknowledge the bug as her brother and calls it a "monster." The ease with which Grete can forget her family duty contributes to the story's generally scathing attitude toward family obligations.
[T]he apple remained imbedded in his flesh […] reminded even his father that Gregor was a member of the family, in spite of his present pathetic and repulsive shape, who could not be treated as an enemy […] on the contrary, it was the commandment of family duty to swallow their disgust and endure him, endure him and nothing more. (3.1)
It's utterly ridiculous that a mere apple could serve as a reminder to the family of their family obligations, but there you have it. The story seems to be saying that family duty is a good thing, which it is insofar as it keeps the other family members from assaulting Gregor. But then the story says that family duty doesn't involve love or affection, but merely the obligation to "endure him and nothing more." The story seems to be saying that family duty basically boils down to suffering the company of people you got stuck with because you happened to be born into their group. Ouch.
Leaning back comfortably in their seats, they discussed their prospects for the time to come, and it seemed on closer examination that these weren't bad at all […] Growing quieter and communicating almost unconsciously through glances, [Mr. and Mrs. Samsa] thought that it would soon be time, too, to find her a good husband. And it was like a confirmation of their new dreams and good intentions when at the end of the ride their daughter got up first and stretched her young body. (3.38)
With Gregor's death, the Samsas appear to be a "normal" family out for a trip to the country. Mr. and Mrs. Samsa's observation that Grete is reaching a marriageable age suggests that, with Grete, a new family will emerge. Of course, given the trajectory of the entire story, one wonders if this new family will be just as dysfunctional as the Samsas.