Well done for noticing this! Yes, it is clear that the way that Gregor is "shut away" into his own room and how, at first, only his sister will enter, and then, not even her, says something very profound about Gregor's standing in the family. Their natural instinct upon discovering the true nature of Gregor's transformation is to lock him away and keep him separate and isolated from themselves. We are told that his parents in particular cannot even bring themselves to enter his room during the first two weeks:
During the first two weeks, the parents could not get themselves to come into his room, and he often heard them expressing their great appreciation of the sister's efforts...
Of course, the way in which Gregor is shut out from their world and the violence with which any trangressions of this boundary are met, such as when his father bombards him with apples, symbolises the way that Gregor is treated as an unwanted outcast, a figure that his family do the best they can to ignore and pretend does not even exist. The real question we have to ask ourselves though is whether this was the case before Gregor's metamorphosis.