Firstly contact the recipient and request a refund, you can also reach out to customer services and ask them to request a refund from that person, however....
Secondly If you sent as friends/family then no one can force them to refund as it was a gift payment, so your only option would be a chargeback if you funded your paypal payment via a credit card BUT its unlikely they will do so either as it was not a payment for goods or services.
If however it was a payment for goods/services and the recipient does not refund then open a dispute for non receipt of item and you may win as they should have nothing to send you.
Advice is voluntary. Kudos / Solution appreciated.