To answer the specific question: Unfortunately, stepparents do not have any legal rights to their stepchildren, even if you consider them to be your own children. Unless you legally adopted these children as your own, you cannot claim guardianship over them.
A stepparent only becomes a stepparent upon marriage to one of the biological parents. You are not a stepparent from a legal perspective if you are only living together with your partner – no matter how long for. Typically, a stepparent doesn't have any legal 'custody' rights to stepchildren.
If the question is, "Can you claim them as a dependent"? The answer is Yes!
Please see this IRS article: Tests for a Qualifying Child
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
