OK, let me take this slowly.
Jack McKay is a 22 year old footballer (currently on loan at Chesterfield). He is not an agent.
Mark McKay is a football agent. Willie McKay WAS a football agent. He is no longer. His company went into liquidation.
Mark McKay's company was employed by Nantes to sell their prize asset. Willie McKay (illegally as it transpires) helped his son, Mark, in touting Sala around the premier league to make a million or two.
Now, which other bit of info about the McKay family would you like.
Yes, Jack is an U23 player with Cardiff. No, he was not acting on Cardiff's behalf as an agent looking to buy a striker. His brother, Mark, was acting on Nantes behalf.
Let me see, how does it go?.....