What is the difference between how is your uncle and your mom and how are your uncle and your mom?

Answer 1

The plural are form is correct because there is a compound subject (uncle and mom). The singular is might be used colloquially with separated nouns or an ellipsis, indicating a delay, e.g. "How is your uncle...and your mom?"

Answer 2

"How is your uncle and your mom" is incorrect grammar. The correct form is "How is your uncle? How is your mom?" On the other hand, "How are your uncle and your mom" is in correct plural form. The correct form should be "How is your uncle? How is your mom?"