(Art by Chyche) Obviously, that possibility is long gone in the main continuity, but what about a timeline where Order 66 never happened and Palpatine was defeated that day? Do you think Ahsoka would be the type to want a family (i.e. a partner and children) or do you think she would want to remain single instead of settling down?
My point is that Ashoka, no longer being a Jedi, was no longer bound by the order's rules. As such, she was free to start a family is she so desired. That said, she could have done so even after order 66. That she apparently didn't do so suggests that she had no such desire.
Master Leem wasn't the only exception to the prohibition against marriage. Jedi Master Ki-Adi-Mundi was also granted an exception due to the low Cerean birthrate. He was allowed by the other Jedi to follow the Cerean custom of polygamous marriage—he had four honor wives and seven daughters.
Actually, I would argue starting a family after Order 66 would be highly irresponsible and dangerous considering the state of the Galaxy at the time. Jedi were being hunted down and killed and their children being taken to be trained as Inquisitors as shown in Darth Vader #19 from 2017. In this issue of the 2017 Marvel Comics run, Darth Vader and two Imperial Inquisitors interrupt the birth of former Jedi Master Eeth Koth’s first child. Vader kills Koth and steals his baby from its mother as they are fleeing. The baby was either taken back to be trained as an Inquisitor or killed. With this knowledge in mind, it’s easier to assume that starting a family would just be too risky for Ahsoka rather than not desired. Regardless, I see where you are coming from and I respect your opinion.
Darth Vader #19