Change some of the text strings in PMPro Sponsored Members Add On via the WP gettext filter.

my_pmpro_gettext_sponsored_members.php

<?php // Do not copy this line

/**
 * This filter will search your codebase for translatable strings and replace when an exact match is found.
 * 
 * Here we're changing 'Number of Seats' to 'Number of Dependents/Spouse/Children' for Sponsored Members.
 * 
 * Add this code to your PMPro Customizations Plugin
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 * Note: When adding to your Customizations Plugin, be careful not to include the opening php tag on line 1 above.
 *
 * @param  string $output_text     this represents the end result
 * @param  string $input_text      what is written in the code that we want to change
 * @param  string $domain          text-domain of the plugin/theme that contains the code
 *
 * @return string                  the result of the text transformation
 */

function my_gettext_membership( $output_text, $input_text, $domain ) {
	if ( ! is_admin() && 'pmpro-sponsored-members' === $domain ) {
		$output_text = str_replace( 'Number of Seats', 'Number of Dependents/Spouse/Children', $output_text );
	}
	return $output_text;
}
add_filter( 'gettext', 'my_gettext_membership', 10, 3 );