Using this you can remove free product from cart when parent product is removed

functions.php

<?php

/**
 * Remove free product from cart when parent product is removed.
 */

function remove_product_from_cart() {
    
    // Run only in the Cart or Checkout Page
    if( is_cart() || is_checkout() ) {
        
        $prod_to_remove     = 13002; // Product ID of Free Product
        $parent_product_id  = 13901; // Product ID of Parent Product
        
        $parent_pro_check   = false;

        // Check in the cart if Parent product is present or not
        
        foreach ( WC()->cart->cart_contents as $prod_in_cart ) {
            // Get the Variation or Product ID
            $prod_id = ( isset( $prod_in_cart['variation_id'] ) && $prod_in_cart['variation_id'] != 0 ) ? $prod_in_cart['variation_id'] : $prod_in_cart['product_id'];
            // Check to see if IDs match
            if ( $parent_product_id == $prod_id ) {
                // Get it's unique ID within the Cart
                $parent_pro_check = true;               
            }
            if ( $prod_to_remove == $prod_id  ) {
                $free_pro_cart_id = WC()->cart->generate_cart_id( $prod_id );
            }
        }

        // If Parent product is not present then remove the free product.
        
        if ( !$parent_pro_check ) { 
            // Remove it from the cart by un-setting it
            unset( WC()->cart->cart_contents[ $free_pro_cart_id ] );             
        }
    }
}
add_action( 'template_redirect', 'remove_product_from_cart' );