We report a study on the shear flow past a square cylinder near a plane wall in presence of a family of eddy-promoting upstream rectangular cylinders in an in-line tandem arrangement to gain a better insight into dependency of the aerodynamic characteristics of both the cylinders on operational dimensionless parameters. The governing equations are solved through a pressure-correction-based iterative algorithm (SIMPLE) with the QUICK scheme for convective terms. Due to the differences in the basic shedding frequencies between a square (downstream) cylinder and a rectangular cylinder (promoter), the major issue of multiple peaks in the spectrum of the fluctuating lift coefficient of the downstream cylinder is addressed and justified with the observed flow patterns. A special attention is paid to search a suitable size of the promoter to produce stronger vortices from the downstream square cylinder in the wake.