If I'm claiming my stepson, do I need to fill the form 8332?

[macuser_22]

No.   The 8332 of only for the custodial parent NOT to claim and allow the non-custodial parent that did not physically  live with the child claim.

[Carl]

The 8332 is only for the biological or "legal" parents of a dependent. It must be completed by the custodial parent (as defined by the IRS) and provided to the non-custodial parent.

Custodial Parent - The one with whom the child lived for more than 182 nights (not days) of the year. If the child lived with both parents for any part of the year, then it's the parent with whom the child lived the most nights of the year. Temporary absences, such as hospital stays, spending the night at a friends house, away for school, summer camp, etc., also count as nights having stayed with the custodial parent, provide the child returns to the custodial parent after the temporary absence. (There are exceptions for the "return to the custodial parent" part. But I"m not getting into that for brevity.)

Non-Custodial Parent - The one with whom the child did not live with for more than 182 nights (not days) of the year.