Not sure if I need to amend as I still haven’t gotten a return and…

No.  You will not need to amend your return for that relationship question/answer.  Whether a brother or step brother the dependency test is the same.  The question relates to him passing test 2 below toward being your dependent as a qualifying relative from Publication 501.  He either needed to live with you all year or be on the list of relatives who did not have to live with you (list below).  

• The person can't be your qualifying child or the qualifying child of any other taxpayer.
• The person either (a) must be related to you in one of the ways listed under Relatives who don't have to live with you, or (b) must live with you all year as a member of your household (and your relationship must not violate local law).
• The person's gross income for the year must be less than $4,700.
• You must provide more than half of the person's total support for the year. 

• Your child, stepchild, or foster child, or a descendant of any of them (for example, your grandchild). (A legally adopted child is considered your child.)
• Your brother, sister, half brother, half sister, stepbrother, or stepsister.
• Your father, mother, grandparent, or other direct ancestor, but not foster parent.
• Your stepfather or stepmother.
• A son or daughter of your brother or sister.
• A son or daughter of your half brother or half sister.
• A brother or sister of your father or mother.
• Your son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law, or sister-in-law.

Any of these relationships that were established by marriage aren't ended by death or divorce.