Hello Supermanqatar,
This is a suggestion for your letter. I have tried to use most of you own words. I do not know the customs of the country you come from, so I do not know how employees address their employers when making such a request as this. Good luck and congratulations on the marriage of your daughter . John
Dear XXX
My name is XXX and I have worked for you since 2005. I am writing to request your support for the coming marriage of one of my twin daughters. I am the father of three girls. My oldest daughter was married recently, and I am still paying off the debts from her marriage. Now it is time to begin making preparations for my next daughter's wedding and, as you know, I suffer from diabetes and am not financially secure. If you could help me and my family with any financial assistance, we would be most grateful. Your generosity would help us overcome a difficult crisis.
Yours faithfully,
XXX