The One Direction star was proudly watching this week as his older sibling graduated from from Sheffield Hallam University.
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"My sister graduated today. She's all clever and that," wrote the 19-year-old, posting a picture on Twitter of himself and his sister in her graduation robes.
Harry and his mum Anne Twist smiled broadly as they watched Gemma pick up a first class honours degree in Science Education with Qualified Teacher Status – which will prepare her for life as a science teacher – during the ceremony at Sheffield City Hall.
The University shared the offical photogrpahers featureing the 1D star, posting: "A special guest attended today's graduation ceremony to see his sister collect her degree! Welcome @Harry_Styles.
"Congratulations to @GemmaAnneStyles on her degree and a warm Sheffield welcome to her brother @Harry_Styles too.
"@GemmaAnneStyles a massive congratulations on your degree! Hope you have a wonderful day with your family."
Gemma marked out the special occasion on her Twitter, writing: "I have never felt clevererer. #graduation."
Harry and Gemma – who have a three-year age gap between them and grew up in Cheshire - have always been close. Harry has Gemma's name tattooed in Hebrew on his left shoulder, and he was often spotted visiting her in Sheffield when his One Direction schedule allowed.
In fact, the star brought Taylor Swift to the city when he was dating her last December.