I am married and currently being sponsored. I have a taxation number when filing taxes. How much HST rebate will my family receive?
If you were a resident of Canada on December 31, 2009 and filed a 2009 tax return, you are treated like anyone else and should get the benefit accordingly, subject to regular eligibility criteria. So, if you would otherwise qualify as a family, you'll get the family benefit amount.
If you weren't yet resident in Canada at that date, here's some information from the Ontario Ministry of Revenue's FAQ: Are there any special rules that apply to new immigrants to Ontario?. Excerpt:
If you were not a resident of Canada on December 31, 2009 and did not file a 2009 income tax return, you must submit a 2009 statement of world income to the CRA to be eligible for the 2010 OSTTB payments. If you immigrated to Canada during 2009 and filed a 2009 income tax return, the CRA may request additional information to ensure eligibility and benefit amounts are accurately calculated.
You must also meet all other eligibility criteria outlined in Q3, including being resident in Ontario on the specified dates. [being May 31, 2010, for the first transition payment; emphasis mine.]