He and I have already agreed never to appear on a TV show and we're not yet married, but his youngest child is actually 6 years olds than I am and both of his children live way in the north. She stayed with us for a month or two and we got on very well (as you might imagine). Even if he and I marry, it wouldn't automatically make me step-mom and that may be for the best. If there were a way to answer questions for a documentary, I would gladly do so, but I couldn't actually appear on one.
acting as a mom to someone almost the same age as you ..... a relationship that blurs the line between parenting and friendship
If you think about it, where a stepmother is close in age to her stepchild, the stepmother's relationship with the stepchild's father will almost certainly have begun after the stepchild was an adult (as otherwise that would mean the stepmother was also not yet an adult, and too young for such a relationship). That will mean there was probably little or no parenting in the usual sense of childcare and guidance based on higher maturity. A close friendship merging into something like being cousins is a more likely outcome.