Half correct. Lee's father in law died October 10, 1857. In his will he mandated that they be freed within 5 years after his death. Lee signed the manumission in late December 1862 or about 2 months late. Since he was busy fighting the rebellion then the fact that he was a few months late is understandable.
Grant's wife had use of several slaves owned by her father, and Missouri records indicate that all the Dent family slaves were freed early in 1863. Further, your claim that Mrs. Grant kept slaves after the end of the rebellion would have been impossible since Missouri ended slavery in January 1865. After that Mrs. Grant didn't live anywhere that slavery was legal, so how could she have retained her slaves until December 1865?
Regardless, she had slaves with her in Grant's camp.