different signatures on different pieces

[shivvy]

I have bought a couple of Boris OKlein and recently bought another 2 from the same place. However although one of the signatures on the most recent ones match my others, the second has an entirely diffent signature. It is quite obviously different so it isn't a case of someone trying to copy a signature.
The person who sold it to me (who seems pretty reputable) says that he buys them direct from the family and that apparently different family members sign them now. (Boris OKlein is dead)
Does this sound feasible or decidedly dodgy?!

[JK2]

Have you read this website info?
http://www.wnutting.com/prints/bios-prints/okl ein.html