Beauty and charm quarks are ideal probes of pertubative Quantum Chromodymanics in proton-proton collisions, owing to their large masses. In this talk the role of multi-parton interactions in the production of doubly-heavy hadrons is discussed. New methods of speeding up simulations with Pythia, a Monte Carlo event generator, when generating events containing heavy quarks have been developed, enabling the production of large samples with multiple heavy-quark pairs. Significantly higher production rates of doubly-heavy hadrons are predicted in models that allow heavy quarks originating from different parton-parton interactions (within the same hadron-hadron collision) to combine to form such hadrons. A set of experimental measurements capable of differentiating these additional contributions are suggested. Quantitative predictions are sensitive to the modelling of colour reconnections.