  We show how to consistently construct initial conditions for the QCD
evolution equations for double parton distribution functions in the pure gluon
case. We use to momentum sum rule for this purpose and a specific form of the
known single gluon distribution function in the MSTW parameterization. The
resulting double gluon distribution satisfies exactly the momentum sum rule and
is parameter free. We also study numerically its evolution with a hard scale
and show the approximate factorization into product of two single gluon
distributions at small values of x, whereas at large values of x the
factorization is always violated in agreement with the sum rule.
