It's not mentioned on Katya or Alona's profile:
Was introduced to tennis at age 5 by father, Vladimir, and mother, Natalia, both tennis coaches ... Currently coached by her mother ... Has two sisters, Valeria and Katerina, also professional tennis players ... Has one cat, Pers ... Speaks Ukrainian, Russian and English ... Enjoys Russian pop music and playing chess ... Likes spending time reading books and listening to music ... Enjoys visiting friends in Cherkasy, Ukraine.
Only two sisters