Let B represent the present age of the boy, F represent the present age of the father, and G represent the present age of the grandfather.

Age Difference Logic

The problem states that the age difference between the boy and his father is the same as the age difference between the father and grandfather. This can be written as:

$F - B = G - F$

Rearranging this equation gives:

$2F = G + B$ (Equation 1)

Past Age Calculation

Five years ago, the grandfather's age was $G - 5$ and the father's age was $F - 5$. The problem states the grandfather was twice as old as the father at that time:

$G - 5 = 2(F - 5)$

Simplify this equation:

$G - 5 = 2F - 10$

$G = 2F - 10 + 5$

$G = 2F - 5$ (Equation 2)

Boy's Age Determination

Now substitute the expression for G from Equation 2 into Equation 1:

$2F = (2F - 5) + B$

Simplify the equation by subtracting $2F$ from both sides:

$0 = -5 + B$

Solve for B:

$B = 5$

Therefore, the present age of the boy is 5 years.