My sons are always in different age groups, due to being 2.5 years apart, and we don't cruise in the time where there is a 2 year gap instead of 3. The first time they actually ended up being combined because the cruise combined the Sharks and Stingrays, which worked out great. Since then my oldest has been in Circle C and my younger son a shark. We board Sunday for the first time having the Circle C and O2 split as they are 12 & 15. To me it has been a non-issue as both kids make their own friends onboard and don't need to socialize with each other most of the time. And I find that they actually spend most of their time outside the clubs doing other things onboard.