Can one keep a wife and mother-in-law as dependents when considering a divorce if one is the sole provider for both medical and housing?

If your not divorced or separated and are just considering (thinking about it) divorce, than it should not be a problem. I would suggest calling the IRS and ask them this question. You don't have to give them your name. If your not comfortable calling the IRS than call one of your local tax preparers like H&R Block and ask.

Often the divorce settlement will include specifics about who may claim whom as dependents, if both parties agree. Generally, in order to claim someone as a dependent you must provide more than 50% of their total support. Thus, if you paid $20,000 to support your wife, you could claim her if her income was $10,000, but not if she made $40,000.