"can an employer pay one employee benefits and not another?" Depending on the facts, employer can legally treat employees differently. For examples, full-time employees likely can participate in benefits not available to part-time employees; employees working in one state may have benefits no available to employees working in another state; employees may be eligible to benefits based on the length of their employment.
Since your post does not have very many facts that may be relevant, it would be difficult to opine whether your husband's employer may or may not be doing anything unlawful.
What your husband can do is review his specific facts with his attorney to see if the attorney can spot anything.