The Portuguese defender admits he does not know whether the Brazilian playmaker will remain at the club, while praising Axel Witsel, who is believed to be on the side's wishlist
The 30-year-old has been linked with a move away from Madrid, having struggled for fitness and form since arriving at the Santiago Bernabeu in 2009 in a €68 million deal.
AC Milan have publicly admitted that they are keen to re-sign Kaka, who played at San Siro between 2003 and 2009, but they have so far failed to reach an agreement with the Blancos, who are reportedly uninterested in loaning out the player.
Questioned about Kaka's situation, Pepe told reporters: "He is a great team-mate and I am happy to share the dressing room, but he is the one to know what his future looks like.
"Today, he is with us and we have to cherish him."
The Portugal international was also asked about his opinion on Benfica midfielder Axel Witsel, who was on Monday linked with a €40 million transfer to Madrid after impressing in his first season at the Estadio da Luz.
"Transfers are something that do not concern me," Pepe said. "Witsel is a great player and he has done very good things at his club.
"If he joins Madrid, he will be welcomed, but if he does not, I would like to wish him the best of luck in the future."