ok so I went and made a new save, speedrunning everything and messing with kink settings - for Rinny to be able to impregnate your character, you have to 1) have finished her quest (the manor) and 2) have at least these kinks turned on: Female partners so she offers to have sex with you when you enter the tower, Futanari so you get the option for her to grow a cock (after refusing everything else, on the second page) and Pregnancy so that you can get pregnant by Riding her to climax (Fertility pill is recommended to increase the chances). Obviously your character also needs to have a vagina, all other parts are optional (but allowed)