My husband wants to adopt my son. My son's father is in the picture but does not pay child support for the child as he is ordered by the court. The biological father got married when I was 2 months pregnant and was not there to sign the birth certificate. Legally, can my husband adopt our son?

Only if the child's biological father consents.

Ask HIM how he feels about it.

If he refuses, then go after him for child support. Many people who do not pay child support are willing to sign away their rights when they find out that it will get them out of child support because a step-parent is adopting.

In order for your husband to adopt your son, the biological father has to give his consent. Without his consent the adoption won't happen.