He did, while Grant kept his, inherited via his wife. The Civil War era is rife with contradictions to the received political narrative such as this.
Inherited from who? Grant's father-in-law didn't die until 1873.
Grant only ever had title to one slave, probably a gift from his father in law. He freed him a couple of years before the War, at a time when he was in dire financial straits, and the price of a slave was somewhere between $25,000 and $100,000 in today’s terms.
Julia Grant may or may not have had title to slaves. Certainly some worked to help her around the house, but it isn’t known if her father transferred title to her, or merely lent them to her. No records.
In any case, they were all freed by MO state action well before the 13th Amendment.
Grant freed the only slave he owned in 1859. The slaves that worked for Julia, were the property of her father Fredrick Dent. She, nor her husband U.S. Grant never owned these slaves.