The term 'relative of -kin' can be broken down into two crossword solutions: ETTE (4 letters) and ULE (3 letters). ETTE is a French suffix used to denote a female relative, such as in the words 'niece' or 'cousinette'. ULE is a suffix used in many languages, including English, to denote a small or diminutive form of a word, such as in the words 'PIGLET' or 'duckling'. Together, these two suffixes can be used to describe a female relative of -kin.