In a way Jenova is his mother (counting one of Lucrecia's lines in Final Fantasy VII it is actually even more than "in a way"). Plus he also found out in the lifestream that Jenova is no Cetra. The lifestream is a big pool of information. Sephiroth knows he has a human mother. That does not mean anything, however. He has more in common with Jenova than with Lucrecia. And I don't know what you mean with "just a nothing" because it is not appopriate for both him and Cloud. Sephiroth has his incredible will and Cloud has his Hero-I will become incredibly strong if I am angry-bonus.
You may troll or dislike him if you want to. But then please be accurate with the information. Otherwise you dislike a Sephiroth who does not "exist" like you describe him.