Let x be the age of Nina.
So, Leonard's age is x - 4.
And Jerome's age is 2x.
Since the sum of their ages is 36, then the equation is x + x - 4 + 2x = 36.
By combining like terms, the equation becomes 4x = 40.
So the value of x which represents the age of Nina is x = 40/4 = <<40/4=10>>10.
Therefore, Leonard is 10 - 4 = <<10-4=6>>6 years old.
#### 6