There are many websites for such requests. Please try using them by "googling" your needs. Additionally, most companies have their own internal formats for all such issues. Check with your HR department. If they don't have one, here is a sample to help you:
To Manager, HR
Ref: Emp ID: ____, Name: _____, Dept/Project: _____
Subject: Approval for Bringing Family
Dear Sir,
I, Mr. ______, have been working in your organization since ____ as __________.
Having now settled into my job and become well-versed with the culture of the UAE, I would like to bring my family. In this context, I would appreciate it if management could provide me with the required approval and support/assistance to obtain my family visa.
Note: (mention "as per my contract" in the above sentence, if you have one). Otherwise, "I would bear all the costs for bringing my family, which may be deducted from my salary."
I look forward to your continued support.
Regards,
PS: You will need to make a separate request for "Live-Out" so that you can get your HRA and "TA" (if you don't want to use company transportation) after your family arrives here.
I hope this is helpful.
Ukmitra