That is a real brain teaser.. It should be my dad.
But, what if my dad died and my mom remarried?.. Then it would be my step dad… but only if he adopted me after the marriage. And what if my mom mever married but is and was ever a single mother.. and if her sister (my aunt) is married to the guy on my couch.. that would make him my uncle. And what if I am adopted by my single mom.. would that make him my step uncle? is that a thing?.. that riddle is totaly fucked up, who thinks of such sick questions?