I tried to research on each of the product releases for the framework and compatible Pega product. There isn't any collaborated document I could find.
Though, the general guideline is to update all the frameworks as well when upgrading Pega base versions.
Let's take a scenario, you have "Insurance Industry Framework 7.1" on Pega 7.1.5 and they are working as expected.
Now, once you upgrade Pega base version, it will have many product/code changes and would contain latest features. Now, if you're updating the framework it would have n number of issues for the older framework version as the latest framework product would exploit all the latest feature of Pega 7.3.1 in this case and thus compatible. While older framework versions won't be having that latest features compatible with Pega base product latest release.
Also, it is advised not to upgrade directly from Pega 7.1.5 to Pega 7.3.1 if you have multiple frameworks built on top of the base product.
Thus advisable to upgrade the base Pega product to Pega 7.2x and install compatible latest framework product on top.
Check for the compatibility and other issues facing, get this upgraded environment(Pega 7.2x framework product on top of Pega 7.2x ) stable by installing all the mandatory Hotfixes for product and framework as well in this environment. Once this environment is stable, upgrade this to latest Framework product 7.31 on top of latest base Pega product 7.3.1.
Hope it gives you a high level idea. Please go through ReleaseNotes and Installation Guide document of each framework to check with compatibility issues.