These car seats are compatible with the Baby Jogger City Mini and City Mini GT Double Strollers from 2015-2018 using an adapter:
Please note these adapters are not compatible with the 2020 City Mini 2 Double or City Mini GT2 Double strollers.
The double stroller holds only one car seat; it does not hold two car seats for twins.
The car seat adapters for the single and double versions of the City Mini and City Mini GT are not interchangeable. See Car Seats Compatible with the City Mini/City Mini GT Single Stroller.