how do i know i'm ready to be a father

i've been casually breeding with my partner for a few years but we've had no success. we're only in our mid 20s so we're not too worried about it. my sister is a few years younger and can just glance in a handsome man's direction and get pregnant. i'm starting to wonder if i'm ever going to be able to be a father. i've had thought of using a fertility clinic but my partner is against it. i know that if i were a mother i would be ready when i'm ready but i have to be on the same page as my partner. how did you know you were ready for the responsibilities that come with being a father.