English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist Alan Turing (1912-1954) did not have a sister named “Kay Turing” (catering), but there are jokes. 
     
“It’s a little known fact, that while the enigma machine codes were being cracked by Alan Turing, his sister Kay provided the tea,  sandwiches and snacks” was posted on Twitter by Wolfy Dempsey on April 28, 2019. “Everyone knows Alan Turing who cracked Enigma codes. But nobody knows his sister Kay, who provided drinks, snacks and sandwiches for him and his colleagues during that time” was posted on Reddit—Jokes on July 25, 2020.
 
“Never realized until today that Karl Marx’s sister, Onya, invented the starting pistol” (Onya Marx = on your marks) is a similar type of joke.
   
   
Wikipedia: Alan Turing
Alan Mathison Turing OBE FRS (/ˈtjʊərɪŋ/; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer. Turing is widely considered to be the father of theoretical computer science and artificial intelligence.
         
Twitter
Wolfy Dempsey
@wolfyd169
Tickled me this one
It’s a little known fact, that while the enigma machine codes were being cracked by Alan Turing, his sister Kay provided the tea,  sandwiches and snacks.
3:40 AM · Apr 28, 2019·Facebook
 
Facebook
Richard Wood
April 28, 2019 ·
It’s a little known fact, that while the enigma machine codes were being cracked by Alan Turing, his sister Kay provided the tea, sandwiches and snacks.
   
Twitter
Gaaaarrrgggghhheth
@chunky666
It’s a little known fact, that while the enigma machine codes were being cracked by Alan Turing, his sister Kay provided the tea, sandwiches and snacks.
8:02 AM · Apr 29, 2019·Twitter for Android
   
Twitter
Ian Anderson
@IanCUBSA
Fun fact!
While the Enigma Machine codes were cracked by Alan Turing, the tea and sandwiches were provided by his sister, Kay..
I thank you😬
11:05 AM · May 1, 2019·Twitter for iPad
 
Reddit—Jokes
Posted by u/RayInRed July 25, 2020
Everyone knows Alan Turing who cracked Enigma codes.
But nobody knows his sister Kay, who provided drinks, snacks and sandwiches for him and his colleagues during that time.
 
Reddit—Jokes
Posted by u/jonafamjoesta September 30, 2020
Everybody knows Alan Turing who cracked the enigma codes
[removed]
 
Twitter
Bob Golen
@BobGolen
Alan Turing is famous for code cracking, but his sister Kay, who provided food and drink to parties, is also well known.
8:32 PM · Sep 30, 2020·Twitter Web App
 
Twitter
The Dad Joke Man
@DadJokeMan
Fun fact of the day…
While Alan Turing was cracking codes in WW2, his sister Kay was providing drinks, snacks and sandwiches for him and his colleagues…
#thursdaymorning
3:26 AM · Mar 25, 2021·Twitter for iPhone
     
Twitter
Robert Wilkinson
@robertwlk
Everyone knows Alan Turing, who cracked the Enigma codes.
Less well known is his sister, Kay, who provided the food and drinks for his team.
2:41 AM · Sep 30, 2021·Twitter for Android
 
Reddit—3amjokes
Posted by u/deadmoby5 March 16, 2022
We all remember Alan Turing for his Enigma Machine…
But let’s not forget his sister Kay, who made the coffee and sandwiches.
Kay Turing…