What is the simplest way to merge two classes in Intellij IDEA?

What is the simplest way to merge two classes in Intellij IDEA?

I have: class Parent {} class Child1 extends Parent{} class Child2 extends
Parent{}
I am using all three classes (especially child classes) everywhere in my
application. Now the decision was made that child classes should be
removed, instead parent class need to hold fields (and methods) from both
child classes. How can I easily get needed result?
Only thing came to my mind is to move all child data to Parent class and
then Ctrl+Shift+R to replace all occurrences of the old classes. Still I
wonder, is there a better way to achieve that?