If the wills of the Husband and First Wife were worded so that they created a binding obligation on one another then they are "Mutual Wills" and upon the death of the first, the survivor is bound to leave the property in accordance with their will, and not to change it. I believe that the assets become subject to a trust, and so the automatic revocation of the will by remarriage should not change the situation. BUT it is extremely unsual for Mutual Wills to be entered into, and apart from such an arrangement the survivor can do whatever they wish with their property.