Something important to know: step children do not automatically inherit from a stepparent simply because of the relationship. There are ways to ensure a step-child inherits — including naming them in a will, adding them to a trust, and, in some cases, adoption (including adult adoption).
If your family includes step-children, this is worth a conversation — it is one of those “almost nobody thinks about it until it’s too late” issues.
Why it’s easy to get wrong: people assume “we were a family for 20 years” creates an inheritance right. It doesn’t. Only a will, trust, beneficiary form, or adoption creates it.
Practical steps: name them explicitly in your will and trusts, list them on retirement/life accounts if you want them included, and consider whether a formal adoption (even adult adoption) matches your goals.