We re-visit the question of whether re-partnering can be an engine for fertility or at least an important counteracting force to the fertility lost due to union dissolution. Our main hypothesis is that cross-country differences in the recovery of births through re-partnering could be one of the key processes that can help explain the gap that separates the two groups of countries that form the "fork" described by the evolution of period fertility rates in industrialized countries. Symptomatically, the group of countries with lowest period and cohort fertility indicators concentrate many of the highest ages at birth (Spain, Ireland, Italy, Greece) and some of the contexts with a stronger resistance to union dissolution (Italy, Poland, Japan, Ireland). Although the question has been explored in the past, we aim to provide a different perspective and to overcome some of the limitations of previous studies by using an agent-based approach. Besides avoiding the difficulties related to the estimation of parameters from micro level survey data, the use of an agent-based model allows for a more detailed and richer representation of the evolution of the connection between union instability and fertility over time and a stronger behavioral foundation of the model. We also propose a comparative approach in which we include Belgium and Spain, two countries with different fertility levels and different mean ages at birth but with similar union dissolution dynamics. Trying to provide an answer to our research question gives us also an opportunity to compare and contrast different simulation approaches, which we hope will contribute to promote the development of this approach to tackle demographic issues.