It will be 18 years this summer since the tragic death of Princess Diana, but her caring nature and good-humored wit continue to live on in her sons. As the Duke and Duchess of Cambridge prepare to welcome royal baby No. 2, Us Weekly takes a look back at some of the heartfelt speeches Prince William and Prince Harry have made about their late mother over the years.

Princess Diana was killed at the age of 36 in a Paris car crash in 1997. Prince William and Harry paid tribute to her at a memorial service in August 2007.

"William and I can separate life into two parts," Harry said in his tearful speech. "There were those years where we were blessed with the physical presence beside us of both our mother and father [Prince Charles]. And then there are the 10 years since our mother's death."

Prince William, for his part, described how Princess Diana's death effected him in January 2014.

"Never being able to say the word 'mummy' again in your life sounds like a small thing. However for many, including me, it is now really just a word. Hollow and evoking only memories," he said at the time. "I too have felt, and still feel, the emptiness."

For more on the late Princess Di, and the fond memories William and Harry shared with her, watch Us Weekly's exclusive video above.