is there any way to access the parent component instance in React?

There’s nothing wrong if you need to access the parent’s props and functions from the children.

The point is that you should never use React internals and undocumented APIs.

First of all, they are likely to change (breaking your code) and, most importantly, there are many other approaches which are cleaner.

Passing props to children

class Parent extends React.Component {

    constructor(props) {
        super(props)

        this.fn = this.fn.bind(this)
    }

    fn() {
        console.log('parent')
    }

    render() {
        return <Child fn={this.fn} />
    }

}

const Child = ({ fn }) => <button onClick={fn}>Click me!</button>

Working example

Using context (if there’s no direct parent/child relation)

class Parent extends React.Component {

    constructor(props) {
        super(props)

        this.fn = this.fn.bind(this)
    }

    getChildContext() {
        return {
            fn: this.fn,
        }
    }

    fn() {
        console.log('parent')
    }

    render() {
        return <Child fn={this.fn} />
    }

}

Parent.childContextTypes = {
    fn: React.PropTypes.func,
}

const Child = (props, { fn }) => <button onClick={fn}>Click me!</button>

Child.contextTypes = {
    fn: React.PropTypes.func,
}

Working example