The Captain's Circle program is exclusive to Princess Cruises only. Loyalty status will not be matched with other lines in the Carnival Corp.portfolio, nor will they honor the perks you've earned as a result of your Princess loyalty status.
The average age of a Celebrity passenger is a tad north of 50. Still, while families with younger children usually gravitate to one of the above-mentioned lines with more family-friendly activities, that doesn't mean you can't bring your kids on a Celebrity cruise.