It depends on the sentence. For example: I heard your mom's going to Germany. A lot of moms will be at the party. Basically, 'mom's' is another way of saying 'mom is' and 'moms' is the plural of...
Your grandmother.
The proper way would be to said 'are mom and dad'.
Check your birth certificate, it will say all kinds of things, such like birthparents, weight.
Why did i your mom is a series of strange events that includes a boy and a girl.........