Discussing the possibility of a move for the 24-year-old, his father, who is also his agent, conceded that he would find it hard to reject any of those three clubs.
"I have had no contact with FC Barcelona. I've just heard the rumour," Hummels senior told Bild.
"Every top footballer has ambitions to play sometime at some European clubs, which you can imagine. These include Real Madrid, FC Barcelona and Manchester United."
Hummels joined Dortmund from Bayern Munich in 2009.