[Solved]-How to declare different state and props for subclasses on react with typescript-Reactjs

You can make ParentComponent generic as well so that the ChildComponent can specify different props and state:

interface ParentProps {
    something: string
}

interface ParentState {
    somethingElse: string
}

export class ParentComponent<TProps extends ParentProps = ParentProps, TState extends ParentState = ParentState>
extends React.Component<TProps, TState> {

    // Component Logic.

    sharedFunction() {
        // Some shared function.
    }
}

interface ChildProps {
    something: string
}

interface ChildState {
    somethingElse: string
}

export class ChildComponent extends ParentComponent<ChildProps, ChildState> {
    // Child component logic.
}