Edited. He was burdened with having to execute his father-in-law's Last Will and Testament, yes. There are existing threads about these circumstances on this forum.
Lee communicated clearly to his son that Custis Parke's slaves were a problem for him. I've never said and I don't think anyone else has, that Robert Lee was, "anti-slavery." Only that he was dubious of the institution. Edited.
You've claimed this before but I'm not aware you've ever produced any actual evidence. If you've got it, please share it with the rest of us.
I've produced the evidence several times. Do me a favor and pay attention so I don't have to repeat myself again.
Douglas Southall Freeman found a will of Lee's filed in Rockbridge County in 1846 showing he owned a woman named Nancy and her children and directing they be freed after his death.
Lee actually ended up with just less than a dozen he owned outright. His mother had thirty slaves distributed among the three sons. He sold some of the slaves and kept the others, renting most of them out. He had Nancy and her children, Letitia, Nat, Billy Gardner, and Philip Meriday.
Lee rented Billy Gardner out to his cousin, Hill Carter. The receipts are in the Shirley Plantation Papers.
The papers have a receipt dated 20 Mar 1827 from Charles Carter Lee "for Ann H. Lee to Hill Carter for hire of a slave named Gardner for 1826." The "H." appears to be a typo in the papers.
There's another receipt dated 1 Jan 1830 [after the death of Lee's mother] for hire of "Gardener" for the years 1829 and 1830, signed by Williams Carter, the executor of Mrs. Lee's will.
Another receipt is there dated 5 Jan 1831 for a check from Hill Carter to Williams Carter, "executor for Anne C. Lee," "for the hire of Gardener."
After that the receipts are from R. E. Lee. There's a receipt dated 10 Feb 1836 from Robert E. Lee to Hill Carter for hire of Gardener for the years 1833-1835.
There are additional receipts in other years from Robert E. Lee to Hill Carter for the hire of Gardener.
Also in the papers is a letter from R. E. Lee to Hill Carter dated 25 Jan 1840 in which Lee writes, "if you have collected any wages for Gardeners of sufficient importance send them to me before I start if convenient, or deposit them to my credit in the Bk. of Va."
There is another letter in the papers from R. E. Lee to Hill Carter dated 1 Feb 1845 in which Lee writes:
"My Dear Cousin Hill[,] I have just re'ce your letter of the 30 ulto: forw'g a check in my favour on the Bank of Virg'a for $30, for the hire of Gardener for the year 1844, for which I am much obliged. The amt. is perfectly satisfactory to me if it is to you & G & you know you have full authority to fix his hire at what you please. Hereafter, if it will be more convenient to you, you can deposit the amount of his hire to my credit in the Bank of Va: & at your leisure notify me of the amt. I can always include it in a draft I make upon them about the beginning of the year on a/c of dividends. The check you have sent me I can no doubt dispose of very conveniently.
We are very glad to hear that you are all well at Shirley. Cousin Eliza Turner left us last Wednesday for Middleburg. Wms. Carter has come down from Baltimore to spend a few days. Chas: Henry brought over his eldest daughter Eugenia to see us since his return from Richm'd. She has grown very tall. Dr. Mason has returned from the West & they were all well at the V.Y. [Vine Yard] whence last heard. I saw Warrington as I passed through.
Rec'd, Arlington 1 Feb 1845, from Hill Carter Esq. of Shirley, thirty dollars in
payment of the hire of my man Gardener for the year 1844 in full to 1845. $30.00 R. E. Lee"
There's also an 1852 letter where Lee was hiring Philip Meriday out.