Helene Katrine /Cordes/

I am looking for any additional information about Helene Katrine /Cordes/ born: 1852 in Germany and died 29 Jan 1893 in Rockville, Tolland, Connecticut.She married Martin /Luetjen/ born 20 May 1850 in Hollen, Bramstedt parish Germany He died 20 Mar 1927 in Rockville, Tolland, Connecticut.
Martin and Helene came to the United States and settled in the Rockville area and raised their large family. I'm looking for parents of Helene and a possible month and date of her birth. I would also like to know of any other family she might have left in Germany.
Any help would be appreciated.
Carol