Is a personal attorney allowed to tell family members of a person in which the lawyer has written the will about the will if they question it?

Except under special circumstances (i.e. to prevent a future crime), which don't seem to apply here, an attorney is ethically bound to maintain his/her client's confidences, and can face discipline from the bar if he/she breaches that confidence.  He/she can also be liable to the client for damages caused by the breach of confidence.