Yes, your son can marry your new wife's daughter. The scenario you're describing is often referred to as a "step-sibling marriage" or a "step-sibling union." In this situation, there is no direct blood relation between your son and your new wife's daughter, as they are only connected through their respective parents' marriage.
From a legal standpoint, step-sibling marriages are generally permitted in many countries and states, but it's essential to verify the specific laws and regulations in your jurisdiction, as they can vary. Additionally, some cultures and societies might have different attitudes and customs regarding such marriages, so it's always a good idea to consider the social implications as well.
If your son and your new wife's daughter are interested in getting married, it is recommended that they consult with legal professionals and make sure they are fully aware of any legal and social implications specific to their location and circumstances.