Corrected entry: In Fuller House we meet Kimmie's younger brother, but in Full House, there was a conversation where Stephanie mentioned in exasperation, "younger sisters" and Kimmie replied "that's why my parents stopped with me."
Phixius
19th Feb 2017
Correction: She must have meant her parents stopped having daughters; no "younger sisters".
Phixius ★
Not sure this explanation makes sense. When parents "stop" after a certain kid is born, it's likely they would try to prevent another pregnancy altogether - not take a chance on what the gender of the next kid would be. A pregnancy here could have easily produced another sister... just happened that this next offspring was a boy.