Secret nikaahs

Q: A Muslim man leading a happy married life, but out of sympathy want to marry another widow woman, and give her a life, but he is doesnt want his first wife to know immediately about his decision of taking up another wife, but later on after an year he would slowly let know his first wife know about the second marriage, so is this cheating? Will his first wife curse the second wife? Should this widow marry this man? Is she becoming a reason of pain for his first wife?