Eugenia has made an excellent find!It certainly explains the dates.From Krasnodar, many landed up in Serbia (Yugoslavia) and then in Austria (Germany), when after WW2 they emigrated across the world, to USA, Canada, Australia & South America, that is the ones that were not repatriatedby the Brits.
Informally these soldiers were referred to as Black Sea or Don Cossacks.Their "origins" were mainly Poltava and Kharkov.
Bad Arolsen should have records for Boris. These archives can providedetails of family's exact experience in Austria/Germany and other personal details such as EXACT PLACE OF BIRTH. Inquiry by immediate family is available for free. Rie, use husband's name as inquirer. All that is needed is to to provide full names (and any other spelling variants) and exact birth dates.
Do not provide more info than that !!! You want the archivists to dig thru the 5 miles of records re DP's, some of which is yet to be digitized. Response can take as little as three days or as much as three months.