Wrong, Sasuke does not own Itachi's body, alive or dead. Just because it's his brother doesn't mean it's his. Itachi was his own person and it's his eyes. Sasuke took those eyes which combined with his power and the result was the EMS, this was not made by Sasuke's power alone but along with Itachi's. Kurama gave Naruto power, as OT described what borrow means, Naruto doesn't return this chakra since he uses it up in his jutsus so how can he return it if he uses it? Borrow means you intend to give back, can't give the chakra back when it's used up.
Itachi eyes doesn't belong to Sasuke either, just like how Kurama is his own living being, Itachi is his own person as well. Both gave their powers to those they wanted. Sasuke and Naruto were give power or took power for themselves. In fact, Obito was the one who had Itachi's eyes and gave them to Sasuke when Sasuke wanted them, after Itachi died, Sasuke blacked out so either way, he wouldn't have had them since Kakashi and Yamato's group would have taken Sasuke if Obito didn't and we don't know if they would have taken Itachi's body, buried it and destroy it since they didn't know the truth about Itachi at that time.
What does Kurama say to Naruto? "If you want me to lend you my power,...."
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Lend means to: (V) give temporarily. (V) bestow a quality on. (v) have certain characteristic of qualities for something. No chakra is temporary since once you use it, it's up and you have to mold more chakra. Naruto is given chakra, he doesn't borrow it; same with Sasuke's eyes, he was given Itachi's eyes, he's not borrowing them nor did he attain his power on his own.