Alex Rosen was the older brother of Leo Rosen.[1]
In 2241, Leo becomes convinced that Alex is having an affair with his wife Sheila, despite his brother's repeated denials Leo persists and eventually alienates himself from the rest of his family and causes Sheila to eventually leave him.
In 2261, having been diagnosed with Felmar's Syndrome, Leo manages to convince Alex to come out to Babylon 5 so that Leo can get the truth out of him. Agreeing only because his brother is dying, Alex meets with his brother and Commercial telepath Lyta Alexander in the Zocalo and submits to a telepathic scan. Lyta confirms that Alex is telling the telling the truth, that he never had an affair with Sheila. Leo is left dejected with his wasted life and Alex, taking pity on his brother manages to convince Sheila (who has since twice re-married and divorced) to come out to Babylon 5 in the hopes of patching things up between them. However, by the time she arrives Leo has fallen under the influence of the Thirdspace artifact and is not himself. Later in the ensuing riots Leo attacks his brother and ex-wife, seriously injuring Alex and is only prevented from killing Sheila by the timely intervention of Minbari attaché Lennier.[2]