Buckle assemblies and associated connectors for use with child seats and other personal restraint systems are disclosed herein. A restraint system configured in accordance with one embodiment of the invention includes shoulder/lap webs which are slideably received in corresponding web connectors. Each of the web connectors includes a tongue portion that is configured to releasably interlock with the other tongue portion before the interlocking tongue portions are simultaneously inserted into the buckle assembly as a unit. The buckle assembly is configured to receive and engage the interlocking tongue portions only when the tongue portions have been properly mated together prior to insertion into the buckle assembly.