Lee got rid of his wife’s slaves before the war started. Grant on the other hand had slaves and didn’t release them till after the war. When asked why he kept them so long he said “good help us hard to find.”
“Although he later served as a general in the Union Army, Grant had control of slaves owned by his wife.[1] He is known to have personally owned only one slave, William Jones, from 1857 to 1859.[2] Grant freed Jones rather than sell him, despite financial need.”
https://en.wikipedia.org/wiki/List_of_Presidents_of_the_United_States_who_owned_slaves
The last of the G.W.P. Custis (Lee’s father in law) slaves were not freed by Lee until Dec 1862.
None of that is true.