I'm not typically the mom who gets teary at the milestones. Back to school, next size up clothes and birthdays don't bother me.

Do I miss my son's fuzzy baby head, hearing first words and his tiny baby clothes? Of course I do. Do I look at him and marvel at how big he is compared to the little kindergartners who walk into school? Yes, I do. However, my gratefulness for sharing these big milestones with him always overshadows that natural ping of nostalgia.

But recently, these milestones have become difficult for me when it comes to my stepdaughters. And this has come as a surprise to me.

As the girls and I grow closer, some of these milestones and big steps we take on are just another reminder of the first several years that I have missed. As each year goes by faster and faster, I'm reminded that I'm not their mom. I wasn't there for baby snuggles or first steps. My husband has shared baby pictures and home videos, but I wasn't there.

My role as step-mom is important, but has different boundaries when it comes to certain experiences. While I get to pack their lunch and hug them at home, I don't get to be the parent sending them off on that first day of school. I may get to be a part of the discussion about ear piercings, but I don't get to experience that landmark pre-teen moment. Feeling sad or nostalgic over moments missed or moments reserved for the "first family" is a common feeling among step-parents I've spoken with. Birthdays are another occasion that can challenge step-parents emotions.

In our blended family, we have taken special care to mark the new milestones of birthdays with new celebrations and traditions, reserving room for the other parents and "first family" to also enjoy the day, while being cautious not to "compete" but to share in the joy. Our kids are so loved, and often get to celebrate more than once with each parent and extended family who look forward to ushering in another year with them.

It's taken me by surprise how emotional I've been about another year, another birthday and another milestone happening in their lives. While I am so glad to be a part of it all, I also feel a sting of reality that I can't go back to get a glimpse of a life that wasn't mine. Even though I want to know who they were, that time is gone and wasn't meant for me.

While these milestones are hard for me as their stepmom, I do take comfort knowing that even though I don't have the memories their first family shared together, this time and the future ahead is paved with memories and experiences yet to be made together.

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