Does the book talk at all about Katczinskys family?

I see no mention of Kat's family in the text.

Stanislaus Katczinsky

Kat, as he is known, is the wise, 40-year-old unofficial leader of Paul's company. A peacetime cobbler, Kat has a knack for making shrewd trades and scrounging up food in seemingly impossible situations. He also seems to have some sympathy with Communism, although this is not well developed in the novel. Though half his age, Paul seems to be closest with Kat of all the soldiers.