An acronym is a word or name formed as an abbreviation from the initial components in a phrase or a word, usually individual letters (as in NATO or laser) and sometimes syllables (as in Benelux). There are no universal standards of the multiple names for such abbreviations and of their orthographic styling.
Son and daughter of your siblings and siblings-in-law. As with uncle and aunt, they're not your nieces and nephews by marriage, they're your nieces and nephews, plain and simple, even if they're your spouse's siblings' kids and don't have a single drop of blood in common with you.
Their children are your parent's first cousins. Therefore your great aunt's niece is your first cousin, once removed, or she may be your mother. 1  Planning the Perfect Spa Day With Your Friends You work hard, and you sure play hard. 2  And, every once in a while, you pamper yourself.