4 Katzes below from Guxhagen in in the Gedenkbuch

Hi,
going to the webpage you added for the Stolpersteine, there is indeed some research done. I let Google do the translation which is quite good and understandable.
I've only corrected a few words. I have at this moment not the time to translate this manually.
By researching the Stolperstone project there, you can find hopefully the citizen-initiative that installed them. They have done the research and might have other resources you can use.
Success!
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The couple Aron and Rosa Katz and their two sons, Walter and Simon were originally from Cuxhagen in the county Melsungen in Hesse.

Aron Katz was born on 25 Born February 1890 in Cuxhagen / County Melsungen. On 2 February 1920, he married Rosa Levi who was one year younger. At least eight children were out of this marriage, including his sons Walter (born 1923) and Simon (b. 1927). It is unclear why the couple in February / March of 1940 moved to Mülheim. Maybe Jewish relatives in Mülheim were the reason. They lived first in 16 Köhle and then moved in September 1941 to the Eppinghofer road 83 . In April 1942 the deportation occurred from Mülheim to the concentration camps Auschwitz and Izbica as destinations. 10 years after the war in February 1955 they were pronounced dead by the District Court at the Ruhr . Time of death was set to 31 December 1945.

Walter Katz was born on 4 March 1923 as the son of Mr and Mrs Aron and Rosa Katz Cuxhagen. Until his parents moved to Mülheim an der Ruhr, he lived in his parents' home. He moved with them to Mülheim, lived just like them first in Köhle 16, then in the Eppinghofer road 83 and finally shared with them the fate of deportation to the extermination camp in April 1942. In July 1955 he was also pronounced dead by the district court Mülheim .

Simon Katz was born on 23 April 1927, the son of Aron and Rosa Katz also born in Hesse Cuxhagen. According to records in the household books of the city of Kassel, he moved in October 1939 together with six brothers and sisters from his birthplace in county Melsungen to the city of Kassel . He was registered there until early March 1940 at the address 22 Rose Street. As the only one of the fraternal household he then moved to Mülheim an der Ruhr, to join his brother, Walter, and their parents. He, too, was deported to Auschwitz in April 1942, and in 1955 by the District Court Mülheim declared dead retroactive to 31 December 1945 .

Thanks for ur help.
It seems we located information about this family in another discussion.
If u are interested - I can add you there

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More info on the Izbica ghetto:
http://chelm.freeyellow.com/izbica.html