I assume you are adding the address, salutation, and signature lines. So here is what I suggest for the body of your letter. First, put your request at the front , then fill in the details.
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Anonymous I regret to inform you that, my father passed away due to old age illness, on 18 th of this month. As you aware of that I have took my short emergency leave when he was hospitalised. I n addition to that I need to extent my leave for ten days more to fulfill my traditional ceremony and I am the only son to do it. So kindly grant me the required leave.