No, Family Sharing is not currently available for CGX subscriptions. The reason for this is that CGX tracks your workouts, week-streaks, progress, and – if your phone's health data is linked – your steps, KCals, and BPM. It's is very much designed to best support one person on their fitness journey. If more than one person were to use the same subscription, this would muddle the data and make it less useful for each of the people using CGX.