Brown (in Borggrefe 2008, p.30) notes that you can really see in this painting that the landscape was added second; you can distinguish Brueghel's precise brushwork from softer, more flowing brushwork of Rottenhammer, and JB's brush strokes obscure the contours of HR's figures. Brueghel also painted the donkey.
Brown suggests, very plausibly, that Rottenhammer used a cartoon to repeat these figures on multiple copper plates which JB then elaborated with landscapes.
Copy of this version sold Munich (Neumeister) September 24, 2003, #334 (copper, 23.5 x 30), previously Sotheby's, London, April 11, 1990; Ertz 1984 #151 as Jan the Younger with tiny poor image. Wiki page.