No, she was not. Grace worked with the deaf and learned lip-reading, etc...
Perhaps the single most powerful incident during her time as First Lady which brought public notice to fellow Americans with disabled sight or blindness was essentially a brief photo opportunity where the First Lady posed with famous deaf author Helen Keller on the South Portico steps.
In the case of Keller, who was also sight-impaired, she was able to “lip-read” only by placing her hand on the First Lady’s lips, and the image was carried in newspapers and on newsreels across the country. Cautious not to exploit her continued professional interest in the work at the Clarke School,
There is also a video of when they first meet... at this link. If they were related it certainly would have said something in the article.. I'd think
anyway, here is the link...
http://www.firstladies.org/biographies/firstladies.aspx?biography=31