George, 1, is holding Charlotte on a white sofa in a series of photos released by the palace on Twitter and taken by their mother, Kate, in mid-May when the princess was around 2 weeks old.
"Prince George and Princess Charlotte together at home #WelcomeToTheFamily," the caption on the series of photos reads.
Charlotte was born May 2 and will be christened in early July.
The princess is the fifth great-grandchild of Queen Elizabeth.
Princess Charlotte is the fourth in line to the throne, behind her grandfather, Prince Charles; her father, Prince William; and her brother, George.