Hi, I'd like to help you with your question.
From your description, it sounds like your wife may be depressed. The loss of her brother and the relationship with her mother, two very significant relationships in her life, are both either damaged or gone. This has probably impacted her much more that she realizes.
One of the best things you can do is to let her know you care and you want to work on things with her. If she does want you involved in counseling, make sure you go. Suggest you both talk to the therapist, even if it's just a few sessions. Give her time to work on whatever is bothering her, but stay in touch with her feelings. Ask her about her sessions and if she will talk to you, listen closely. Touch her gently and tell her you care about how she feels.
You can also work on how to help her through self help. There are many ways you can connect with her. Here are some very good websites and books to get you started:
http://www.marriagetoday.com/- this site may talk about infidelity, but the basic principles apply in helping your marriage become stronger.
The Seven Principles for Making Marriage Work: A Practical Guide from the Country's Foremost Relationship Expert by John M. Gottman and Nan Silver
Fighting for Your Marriage: A Deluxe Revised Edition of the Classic Best-seller for Enhancing Marriage and Preventing Divorce by Howard J. Markman, Scott M. Stanley and Susan L. Blumberg
The Marriage Clinic: A Scientifically Based Marital Therapy by John Mordechai Gottman
You can find these books on Amazon.com or your local library may have them for you.
You may also want to work on the time you both spend together. It sounds like you live separate lives, which even in the best marriages will cause you to grow apart. Make time to do things you enjoy together. Go out to dinner without the kids, take your wife to a movie. Have a date night. Be interested in what she is doing. Ask her about herself. Do something small for her, like set up a bath with rose petals or make her a cup of tea. It may take some doing, but if she still has feelings about your marriage, as I suspect she does, she will come around.
Let me know if I can help in any other way,