Conger Research Challenge

On page 39a of The Conger Family of America, Vol. 1, Maxine Leonard states:

CHARLES CURTIS CONGER 1851 married Abbie Grant, niece of Ulysses S. Grant.

There is no source citation. As of September 2014 I wasn't able to find any information on the Internet that would support this relationship.

Here's what I know:

1. Charles Curtis Conger was born on 23 Jan 1851 in Oneida, Knox Co., IL.
2. Abigail "Abby or Abbie" Adelia Grant was born on 21 Apr 1853.
3. The couple had two children: Norma Grant Conger and Clara Hurd Conger.
4. Ulysses S. Grant was a Civil War General and later President of the United States.
5. U.S. Grant had two brothers: Samuel Simpson Grant and Orville Lynch Grant.  It appears that Samuel might not have married.  Orville married but I didn't see any children listed.

Here's my Conger Research Challenge.

1. Link Abigail Adelia Grant to one of the brothers of U.S. Grant.
2. Provide the name of Abigail's mother.
3. Cite sources to prove the link.

Can you help me solve this challenge?

Dick Henthorn

9 September 2014