Vronsky has never had a family life; he essentially grew up in the Corps of Pages, where he became a brilliant officer. He is not aware that he has been leading Kitty on, since marriage doesn’t seem like a possibility to him. Since he has been having a fun time with Kitty, he assumes that she has been having fun as well, and he hasn’t considered that there might be deeper expectations or consequences.
Vronsky is rich, handsome, and brilliant––but he has never thought about settling down to raise a family, and indeed, he has never considered what the consequences of his actions might be. As long as he is taking pleasure and everything seems to be going smoothly, he assumes that all is well for everyone else, too. He is not a villain, but his casual neglect of others can be harmful to others.