How does Macbeth feel about killing Macduff's and Banquo's family?

Surprisingly little. After killing Duncan, his feelings seem to have been numbed so that he does not feel any remorse for his killings. He does feel fear, however, which killing more people only makes worse. On the other had he says to Macduff, "my soul is too much charged with blood of thine already" which suggests that even at this late date, he feels some remorse about the murders.