If 'etc.' is at the end of a sentence are there 2 periods?

no, there is only one.

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I can't think of any example where ending a sentence with two periods would be necessary. Not even following the last Word in a sentence that is being quoted within parentheses would I expect one to employ two periods. One, I humbly submit, is all that's ever needed.

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Placing more than one punctuation mark at the end of a sentence is superfluous.

It is a rule of punctuation that there be only one form of "end punctuation" to a sentence. Whether the end punctuation be a period, question mark or exclamation point, only one is required.

The rule applies also when the punctuation mark appears within parentheses or quotation marks; a second punctuation mark is both unnecessary and inappropriate.