that tells me you prematurely split something. I worked at a high scale, high available system with multiple dozens of teams, each with several repos. If we had to sync changes across repos, we joined the repos because they were, well, joined. In the early days, we had shared libraries and keeping those in sync was a pita. Then we realized we should not be doing what we were doing.
The flow should be: (1) update a library and release it, preferring backwards compatible changes or a new major version; (2) code that wants/needs the new functionality updates the usage at its leisure. If you are having to keep multiple repos "in sync" with each other, yes, you picked the wrong abstraction. If the downstream repo(s) need to always be on the latest and greatest version of the library, the library code should be vendored with the calling code.