Prince Harry says he is "delighted" Prince William "finally popped the question" and he is glad Kate Middleton is becoming part of the Royal Family.
The prince told German newspaper Bild he had "always wanted a sister and now [had] one" ahead of a trip to Berlin.
The 26-year-old is due to receive an award recognising his charity work on German television on Saturday.
Prince Harry told the paper his mother, Diana, Princess of Wales, had been an "inspiration".
"She did so much fantastic work with her charities and I think people particularly warmed to her because of the way she was able to put them at ease, no matter what environment or situation they were in.
"Her compassion was obvious to see. Like her, I realise I am in a privileged position as a member of the Royal Family, and I have to use what I have been given to highlight important issues," he said.
He said he had also "learnt an awful lot" from his father who had worked with "charities for decades", as well as his brother.
"I am still just starting out with my charity work, but if I could follow the fantastic charitable work they have done, and continue to do, then I don't think I can go far wrong."
Speaking about Prince William's engagement to Miss Middleton, the prince said he was "absolutely delighted".
"I've always wanted a sister and now I've got one. I've known Kate for years, and it's fantastic that she is becoming part of the family," he said.
Prince Harry is due to be presented with a Golden Heart during Ein Herz fur Kinder - A Heart for Children - during Germany's largest television fundraising gala.
The prince is patron of a number of children's and humanitarian charities - including Sentebale, an organisation he co-founded in 2006 to help disadvantaged youngsters in Lesotho in Africa.
Speaking about the country, he said: "There is a great deal that I am proud of that Sentebale has achieved over the past few years and the difference we have made to so many children, but I am also impatient and want to do more and more.
"Through our strategy of working at a grass roots level, we ensure that our work, helping the children, is locally driven, locally delivered and locally appropriate."
In the interview he also joked about the football rivalry between Britain and Germany.
"I know the German people are always very welcoming so I'm looking forward to meeting Berliners... as long as nobody mentions anything about the football," he said.