Age mixing plays an important role in the formation of relationships within computer simulations of Human Immunodeficiency Virus (HIV) transmission. We present and analyze an algorithm that takes individuals seeking a heterosexual relationship, and forms pairs of a desired joint age mixing distribution. The rate at which eligible individuals seek relationships varies by age group and gender, and is actively manipulated using feedforward and feedback controls to ensure throughput and avoid instability. Theoretical results guarantee that the relationships formed will match the desired joint distribution, in expectation, while simultaneously avoiding throughput problems due to storage and stochastic variations. Results demonstrate the utility and effectiveness of the network generation process within a detailed stochastic agent-based computer model of HIV.