This is a mash-up of the words 'Kismet' meaning 'fated' or 'destined' and 'Nemesis', which i
hope we all know means 'rival' etc
so together, a Kismesis, (or plural, as in 'a pair of Kismeses' taking after the plural of nemesis) is your fated rival; or
even, some would say, your Serendipitous Rival. Kismessitude is also sometimes called 'Black Romance' or 'Caliginous Romance' (calidinous meaning misty,
dim; obscure,
dark) in that it is
dark and hateful, so lets not forget the romantic aspect, as in competing with someone so often, tensions run high... including sexual tension (eyebrow-wiggle)
now that you know what a Kismesis is, go
get your black-mack on
Antithesis: Matesprit