First of all thank you for the myriad of information that you guys are giving out, it's an eye opener
and an invaluable source of help!! I applied for a FP for my recently widowed Mother In Law (MIL). I have literally just returned after the funeral etc and applied for a EEA FP with the required docs for which I though was a straightforward case. Unfortunatley it came back rejected!!
A bit of background info for you guys:
I am french by birth , living here for a good 25 odd years. My wife was an indian national who later naturalised as british. I have only had the chance of sending 1 money transfer to MIL since arriving back for her day to day living expenses.
The documents sent were as followed:
-My MIL Passport
-A copy of my passport
-A copy of the entry and exit stamps in my passport to show the travel date
-My marriage certificate and my wifes birth certificate (to show link back to MIL) as the spelling differs slightly I also put in an affidavit to say they are both the same person
-Utility Bill
-3 x P60s along with 3 payslips
-My FIL's death certificate
-Proof of remittance sent
-Proof of remittance received
-A letter from me to the ECO asking my MIL to JOIN me here
-A TB Certificate (I didnt want to risk it)
-A Joint tenancy agreement
I received a rather quick reply from UKVI's office here - they refused it on two grounds
They have acknowledge that I am the Son in law and treating my MIL as a core family member. No interview was carried out or asked for any more info.
The grounds for refusal are as follows
First para acknowledges that I am exercising treaty rights in the UK
second para .. however, you have provided no historical documentary evidence of their birth or DNA test results to show that you and your sponsor are related as claimed. In view of this failure to provide satisfactory evidence. I am not satisfied that you are the family member of an EEA national in accordance with Regulation 7 of the immigration....
DNA TEST between me and my MIL??? .. That's bound to come back as a no match!! 
Surely the documents that I provided above should satisfy the link - ie my passport - our marriage certificate - my wife's birth certificate - along with an affidavit. 3rd para acknowledges evidence of money transfer but ends......I am not satisfied that you have demonstrated that this money pays for your essential needs...
4th para On the evidence submitted in support of your application and on the balance of probability I am not satisfied that you are related as claimed or mainly financially dependent on your sponsor, or if you are, I am not satisfied that it is a depedency of necessity rather than choice. I am therefore not satisfied that you are an extended family member in accordance with Regulation 7....
I am ready to tear my hair out!!! Please help!!!