From Robert Burlingame - the census records show a variety of spelling of the name.  For Robert Howren, it is:
1840 Robert Howrin
1850 Robert Howard
1860 Robert Howern
1870 Robert Howering
1880 Robert Howren
All the above are the same person.
 
Many of Robert Howren's children lived in Washington Co Tennessee, and I have traced most of them, particularly if they have kept the name Howren.  Howren is the correct spelling of the name, and all the descendants spell the name as Howren.  I have not found any exceptions to this statement.
 
I am not an expert on the Salts family, so I could easily make an error here.  I would welcome any correction.
 
The 1860 census has Sarah Salts living with Robert and Catherine Howren.  So it is likely that Sarah is Catherine Howren's mother.  I have assumed that, but I have no other proof. 
 
I have, therefore assumed that Catherine's maiden name was Salts.
 
In my database, I have Samuel Salts as the brother of Catherine Salts Howren.  I don't have a source in my documentation. It is possible that it came from a source on the internet that has been subsequently removed.  I note that the 1850 census shows Samuel Salts as being next to Robert Howren.  It is fairly certain that Samuel Salts is closely related to Catherine Salts Howren, but one cannot draw the conclusion that they are brother/sister. 
 
I looked at your link at the "Salts Family", but I could not find any reference to Robert Howard.
 
The spelling should be corrected to "Robert Howren".

1840 Census - 6th Regiment, Washington County, Tennessee Census
Page 121
SALTS, Samuel 1 male 10 – 15
HOWRIN, Robert 1 male 15-20 [ listed 3 names above Samuel]
STARNES, Fredrick and Elizabeth (Salts) are listed 6 names below Samuel.
Page 119
HOWRIN, Benjamin [probably Robert’s father]
DELASHMET, Moses and Nancy (Salts)
SALTS, Jessee

Family 1234
1850 - Subdivision 4, Washington County, Tennessee -indexed under Samuel Salls
SALTS, Samuel 23 m nail cutter TN
SALTS, Caroline 23
SALTS, Martha J. 4
SALTS, W. B. 3
SALTS, Manerva 1
Family 1235 - living next door
1850 - Subdivision 4, Washington County, Tennessee
HOWARD, Robert 29 m nail cutter TN
HOWARD, Catherine 28 f TN
HOWARD, Sarah J. 7 f TN
HOWARD, James 5 m TN

1860 - District 4, Washington County, Tennessee1273
HOWERN, Robert 41 mill wright TN
HOWERN, Catharine 40 TN
HOWERN, Sarah J. 16 TN
HOWERN, James 14 TN
HOWERN, Nance 10 f TN
HOWERN, Robert 8 m TN
HOWERN, Alexander 5 m TN
HOWERN, Eliza 5/12 f TN
SALTS, Sarah 62 f NC

1870 - District 6, Washington County, Tennessee
34/33 family / household
HOWERING, Robert 49 TN
HOWERING, Catherine 47 TN
HOWERING, Robert 16 TN
HOWERING, Nancy 19 TN
HOWERING, Alexander 13 TN
HOWERING, Eliza 10 TN
HOWERING, Benjamine 8 TN
HOWERING, James 24 TN
HOWERING, Eva 20 TN
35/34 family / household
FREEMAN, James 30 TN
FREEMAN, Matilda 30 (Rogers) VA
FREEMAN, William 11 TN
FREEMAN, Alexander 7 TN
FREEMAN, Elizabeth 4 TN
FREEMAN, Nancy 2 TN
FREEMAN, Martha 43 NC
FREEMAN, Jane 14 TN