My hunch is, if you've been a fit mom from the start or began this fit mom journey when your kids were old enough to give you dirty looks, there's been another mom in your life who inspired you.
Just a hunch.
The fit mom mentor is slightly different from a fitness mentor, the obvious being she is a mom. Like a fitness mentor, she shows you the ropes (directly or indirectly) for a particular activity, motivates you to get out the door, or inspires you to take your fitness further than you otherwise would (even if it's not as far as she goes). The added layer for the fit mom mentor is that she does all this with kids on the side (or along with her) so that you see having children is no excuse to forgo working up a sweat or setting personal goals. You love her for this and, perhaps, sometimes curse her because this means, of course, you can and should do it, too.
In the Balancing Motherhood and Fitness survey from last month, the majority of respondents had someone who kept them going, if not with their physical presence--usually a training partner--then merely as an example; someone they aspire to be like. It thrills me to no end that many of the fit moms who took the survey sited their own mom as their fit mom mentor. I am certain that my own road to fitness began that day my mom took me to the gym for the first time (my mom has some serious guns).