public Register[] family() {
		for (int i = 0; i != ALL_FAMILIES.length; ++i) {
			Register[] candidate = ALL_FAMILIES[i];
			for (int j = 0; j != candidate.length; ++j) {
				if (candidate[j] == this) {
					return candidate;
				}
			}
		}
		throw new IllegalArgumentException("Register does not have family?");
	}