Good afternoon Diana,
I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today.
Provided that you have a signed lease agreement with the landlord that specifically stated that your rights to move in would be effective on May 15th, then yes, you may sue for Breach of Contract and collect as damages all reasonable expenses that you have incurred for lodging since the move in date. Damages for meals is a bit more problematic because food was not included with the rental---but only the means to store it and prepare it so while you will want to ask the judge to award you the costs of meals, you will have to settle for loss of use of the storage and cooking facilities in the rental and not your actual cost of restaurant food.
If you father in law is not listed on the lease agreement as one of the intended tenants for the rental unit, but rather he was simply going to be a visiting guest, unfortunately his expenses will not be collectible by you in a suit for breach of contract. However, if he is listed on the rental agreement as an intended full time tenant, then you could sue to collect for his expenses as well to the extent that you have paid for them. If he paid for them himself, then he would have to be the one to sue, but he could be listed as a plaintiff in the same suit that you file for damages in the court.
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I wish you and yours the best in 2016,