Sephiroth knows, knows, that he is likely to get a negative response here. That if he goes to Cloud, tries to comfort him, that Cloud is likely to reject him, maybe even violently - from the old trauma from Nibelheim, from the old-made-new trauma of this realization and their grim connection, from just being the (perceived) source of this new misery, from simply not being able to handle any more than he already is. Any or all of those things. The reasons Cloud could have for actually accepting concern for and closeness from him are perishingly few, the reasons he would shove Sephiroth away from him - physically and/or figuratively, and shoving is probably the best case scenario - overwhelmingly numerous and persuasive.

Sephiroth knows all this, and moves forward anyway. He can't not.

He kneels down in front of Cloud, lightly touching his arms. "I know." He knows better than perhaps anyone might, he supposes, except perhaps Zack or the other victims who survived Nibelheim. "But you're all right now, Cloud. He's not here..."