I'm I raising my children too close?

The relationship they have sounds lovely and heart warming, and for now, at this age, not unhealthy. The sad truth is that the time will probably come when one (probably the eldest) will reach a point where she thinks it's not 'cool' to hang out and love being with your siblings as they get given more freedom to go out with friends by themselves which for the other sibling may be upsetting at first but they will re adjust and the closeness that was there when they were younger won't ever be gone forever. For now I say enjoy it while it lasts and they're still young.