If you use "either", then this means one of them, but not the other, is coming - most likely.
Either of my parents are coming.
Either of my parents will come.
Either of my parents can come.
I would recommend not using "either" in this way. It's not typical language. It sounds a bit odd or strange.
Someone's bound to bring it up, so here it is:
When followed by of and a plural noun, either is often used with a plural verb: Either of the parties have enough support to form a government.
either: Definition from Answers.com
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