You have another issue: can your stepdad really claim you? A stepdad is the same as a dad, for tax purposes, so that's not an issue. You say "I started work in October" . If you made more than $4050 for the year, you cannot be claimed; unless you are under age 24 and  were a full time student for at least parts of 5 months.

Good catch.

I only worked part time so it was less than $4050.

Your boyfriend has the right to claim his own child your step dad can only claim him if you give him permission or heif  has custody

Yes, he is the biological father. And my stepdad makes more than both of us.

The parent has more right than the grandparent or step grandparent.

That said, any relative in the household can claim the kid. It may be worthwhile to do test returns to see which way the family comes out best. This tool may be helpful: https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1. 

See the requirements to claim a child below:

To claim the child, the taxpayer  must meet these requirements to be a Qualifying Child or Qualifying Relative:

Under the qualifying child rules:

• Your qualifying dependent must live with you for more than half the year.
• The qualifying dependent must be one of these:
• Under age 19 at the end of the year and younger than you (or your spouse if married filing jointly)
• Under age 24 at the end of the tax year and younger than you (or your spouse if married filing jointly)
• Permanently and totally disabled
• The qualifying dependent can’t have provided more than half of his or her own support.

Under the qualifying relative rules:

• Not qualify as somebody else’s qualifying child or qualifying relative
• Live with you the entire year (365 days) or be one of these:
• Your child, stepchild, foster child, or a descendant of any of them
• Your brother, sister, half brother, half sister, stepbrother, or stepsister or a descendant of any of them
• Your father, mother, grandparent, or stepparent, but not a foster parent
• Your son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law, or sister-in-law
• Your uncle, aunt, nephew, or niece
• Earn less than $4,050
• Receive more than half of his or her support for the year from you

To claim a dependent, these must also be true:

• He or she can only have filed jointly with his or her spouse to claim a refund of the taxes withheld. Also, if he or she were to have filed separately from his or her spouse, neither would have owed taxes.
• The dependent is one of these:
• U.S. citizen
• U.S. resident alien
• U.S. national
• Resident of Canada or Mexico

You can’t qualify as a dependent on someone else’s return. This is true even if the other person doesn’t clai

As you can see, it is important who the child lived with. That is the person that usually gets to claim the child unless there is a divorce decree that says otherwise.

She lived with both her father and her "step grandfather"