The answer to this question will hinge on many more facts than are disclosed in this question. Generally, one person cannot bind another person legally unless the first person gave the second person permission to do so. Usually permission is given with a document called a power of attorney. Without a power of attorney, the signature of one person usually cannot bind another person.
Another issue to consider is under the doctrine of agency. Generally, an agent can bind the principle. For instance, a lawyer who acts as an agent for a client can bind the client.
There are too many open issues with your question that cannot be properly answered with a short answer online. You should consult with an attorney to discuss more specifics with your situation.
The above answer is provided for information purposes only and is not intended to create an attorney-client relationship.