Being a step-parent is a tough role to fill. You can have all the best intentions in the world and still end up alienating the child because at the end of the day, it's not up to you, it's up to them. Step-parents can have beautiful relationships with the kids in their lives, but just like any friendship, you have to let it develop naturally. If you force it, it's cringe at best, and isolating at worst. Kids are fickle.
Of course, it doesn't help that the media is full of horrible depictions of step-parents, from the classic Cinderella character to the Dursleys in Harry Potter. They're always portrayed as wicked and unfeeling. It's an uphill battle for real step-parents to disprove. But the key to success is never forcing it, like in the case of this recent Reddit story that pulled the curtain back on an unfortunately common stepmom case. Stepmoms, read up.