hoffgirlfriend460cropbright.jpgCashman Photo

David Hasselhoff is expanding his much younger girlfriend Hayley Roberts' musical knowledge by taking the hot blonde to see Donny & Marie's show at Flamingo Las Vegas.

After the show, the 59-year-old former Night Rider star and 31-year-old Hayley met up with the famous brother-sister duo backstage to snap the above photo. Looks like a fun group!

Although they're smiling in this photo, just last week Roberts and Hasselhoff reportedly got into a heated argument at the Wynn resort in Vegas forcing security to break up the fight. Must now be water under the bridge.

See Donny and David horsing around ... after the jump.