this should be no problem. They can run both as isolated instances. The only possible 'issue' you could encounter is that tools that where supported are not anymore.
e.g. SQL Version 2008 R2 is not supported in K13 but it was in K12. Or the minimum required version of Microsoft .NET Framework is now 4.8.
But for these things you can either run them next to each other (you can have multiple .NET frameworks installed), or there are higher SQL versions that support both.
See Breaking changes in K13 release notes: