...or maybe the Lady is actually Rincewind's Mother/Creator
Rincewind's self-proclaimed middle name is Luck (first name Bad)
He is described as a "luck sink" in Unseen Academicals (and what do you do in a sink? rinse! not a clue, just a pun)
He gets into dangerous situations (bad luck) but then always survives them (good luck)
Rincewind's mother ran away before he was born-- if taken literally, then this could only occur with magic, so his mother was either a time travelling witch or a goddess
He kept encountering the Number 8, which is considered unlucky to wizards due to the Octavo; 8 looks like an infinity symbol and also sort of like a woman's body -- who is an immortal 'woman'? The Lady (this one is kind of a stretch, I admit)
The Lady has green eyes, some of the official art portrays Rincewind with green eyes
But then who is Rincewind's father if the Lady is his mother? (if a father is even required in this situation) Possible candidates include:
Fate - an enemies-to-rivals-who-fuck romance that produced a child, Rincewind, whose fate is adventure and danger but who also has the good luck to survive it all. (yeah, Fate tried to get Rincewind and Twoflower killed, but maybe he didn't know or even didn't care Rincewind was his son)
Lavaeolus, the Rinser of Winds - who had to go on an oddessey (misspelling intentional) to get home. Maybe the Lady played the role of Circe in his journey, and Rincewind was born as a result (many years in the future, because the Lady decided she needed him at that time for her games with the other gods)
Bill Rincewind - who then, upon finding out he--who as a wizard is meant to be celibate--got a woman pregnant, went out for milk/cigarettes/beer and took the 'wrong' boat, ending up in Fourecks (this is a crack theory)