Is there a way to ensure that future implementation of an interface will also extend a class

So I have an abstract class and two final classes that extend it. The abstract class is also an implementation of an interface. So what I have to do is - remove one of the two child classes and add an interface so that people can still come in with their own implementations. BUT the tricky moment is - is there a way to ensure that whoever implements the new interface is going to extend the abstract class or the only way is to document an implementation requirement? They need to exted it as otherwise it won' be functioning.