It is never clearly stated in the animated series that Cyclops and Havok are indeed long-lost brothers, though it is hinted at since they develop an instant rivalry and neither brother's powers affect the other; a fact which is also seen in the comics.
It is never openly stated in the animated series that Cyclops and Havok are indeed long-lost brothers, though Alex's existance is revealed in flashbacks. When the two meet they develop an instant rivalry and neither brother's powers affect the other; a fact which is also seen in the comics.