Two bubbles in conjunct condition are often encountered in high-viscosity liquids, but have received very little attention in the literature. The conjunct bubbles rise together with unchanged shapes and constant velocities, showing some unique properties compared to single bubbles. The current research built on the previous work of Cai et al.,([1]) and extended the bubble size ratio (kappa) to the range 1.0-1.2. The formation and motion characteristics of conjunct bubbles made by direct collision of two in-line bubbles were investigated, including the effects of bubble volume, bubble size ratio, and liquid viscosity. Models for the conjunct bubbles and the single bubbles were provided for predicting the projected area diameters and the rising velocities respectively, and the predicted values closely agreed with the measurements in glycerol-water solutions with Morton numbers in the range of 1.690-661.8. The dynamic forces on the conjunct bubbles were analyzed, and a succinct algorithm was proposed for calculating the drag forces on the conjunct bubbles and the interaction force between the two bubbles.