I have not found any additional notes on James, Sidney, or Temple yet.However, I also got the same data as you from the 1850 Census for Jefferson Co., Louisville, KY.
The ???? Gwathmey in your posting would be Fortunas Cosby Gwathmeyb. April 19,1813, (brother of Sidney), Bridget would be his wife Bridget M. (nee Lyons) b. 1820 and John b. 1842 is there son John Temple Gwathmey.
I show James's and Sidney's marriage date as being 1837.I also believe that James was a minister, possably of the M.E. Church.
I took a notebook full of notes on the Gwathmey, Clark, and Rogers families last year while at the Filson Library and I will track them down try to se if I have any additional information on James or Sidney.
I would be pleased to add any additional information on this family to my files if you would like to share your data.You can contact me by e-mail if you would like.