Yes, of course they should be concerned -- and not only concerned, but also expressing it to you. The Bible says, "Carry each other's burdens, and in this way you will fulfill the law of Christ" (Galatians 6:2).
Have you asked yourself why don't they say anything? One reason might be because they're too wrapped up in their own concerns, and simply don't think about the needs of others as much as they should. If so, they're falling short of what God wants them to be, because Christ's command for us to love others is very clear. He said, "My command is this: Love each other as I have loved you" (John 15:12).
But don't be too harsh on them or allow yourself to become bitter over their apparent lack of concern. In reality, they simply may be embarrassed to say anything to you, fearing they might hurt you or offend you. After all, have you ever asked any of your friends at church to share your heartaches and pray for your family? Your own reluctance to share your feelings may be part of the problem.
The most important thing I can tell you, however, is this: God has not forgotten you and your son. He knows what you're going through, and He loves you and wants to help you. Put your lives into Christ's hands, and then ask Him to bring your family closer to each other -- and to Christ.