50 Cent has branded his current feud with his ex Shaniqua Tompkins his "toughest" challenge to date - because their strained relationship is having a negative affect on their young son.

The rapper and his former lover have been battling in court after 50 Cent's home in Long Island, New York - where Tompkins and 11-year-old Marquise had been residing - was destroyed in May in what police have called a "suspicious" fire.

The In Da Club star, real name Curtis Jackson, is suing Tompkins for defamation after she accused him of starting the blaze.

She was recently granted a restraining order against her ex, preventing the star from being on the same premises as her.

But, while the court order does not stop 50 Cent from seeing their son, he insists it has put Marquise in a difficult situation - because the boy doesn't want to upset his mum by spending time with his dad.

50 Cent tells MTV.com, "I think he doesn't want his mom to feel like he's a traitor. ...The time I spent away is the time he developed this thing he's afraid to break with her. There's nothing you can do about that. This is the toughest (thing I've had to face), because he's my motivation."