Here at eNotes, we are unfortunately not allowed to do your assignment for you. Because of this, I cannot create the essay that you need. I can, however, offer some points that may be helpful in guiding your own essay. Feel free to use these points, but put your own spin on them or just use them as jumping off points for other thoughts.
Family is an incredibly important concept in The Metamorphosis, one that guides a lot of the plot and the interactions. There are a few important things to keep in mind. The first is that all of the family members are quite shocked by his transformation, but they all interact with him differently. His mother is mostly sad, his father is mostly mad, and his sister is wary but helpful. In this way, we can think of his metamorphosis as a means of seeing how his family members really feel about him. One of the biggest takeaways is that his sister loves him unconditionally. Even though there has been a change, she goes out of her to bring him food and assist him. His father, on the other hand, is shown to be more surface-oriented; we can extrapolate from this that he desires his son to be perfect, presentable and "ideal."
A good thesis for a paper like this could involve the concept of Gregor's metamorphosis as a way of getting to the family's true feelings about him. It shows that families can be superficial and conditional, even though they are supposed to be incredibly tightly-knit and not care about external factors. It reminds me of the scene in Mary Shelley's Frankenstein, when the monster is rejected by the blind man he has befriended because of his appearance. It shows that human beings are cruel and judgmental. That's just one opinion you could have; you could also try to focus on his sister and show that family conquers all and that human beings care for one another.
In the end, I think it would be wisest to pick one opinion on the concept of family, find supporting evidence via how Gregor's family reacts to him in insect form, and go from there. I hope this helps a bit—good luck!