I have been with my boyfriend now for 7 years and we plan on getting married next year in 2016 the problem is he wants to adopt my 19 year old son who has a baby on the way so the baby can have his last name and so can my son. The baby is due in June. How do I go about this?Please give details for we don't have much time to play around on this.

Has the mother agreed to the name? You didnt mention if he is married or not to the mother. Also your son could seek a name change anytime he likes so long as it runs consistent with local laws. Depending on where you are some places do not allow for adult adoptions.

OP is talking about an "adult adoption", as opposed to an adoption of a child. If allowed in your state, the adult's son's natural father may not need to consent, and other rules may be easier too. But I assume that the OP would want to remain the son's mother. In that case, it is in some respects still a step-parent adoption, and as such the OP and her fiancé might still need to be married.

Consult an attorney in your jurisdiction, but I agree with Cdad: a name-change may be much easier.

I agree that the first order of business here is the mother. Unless your son is married to her, she has the say over how the child is named. So even if your son does change his name, she doesn't have to go along.

Even if they are married, she may have to agree to legally change her name.

And yes I agree that your son petitioning the court for a name change would be a lot easier than an adoption. Depending on local laws (any question on law needs your general locale as laws vary by area), you may have to be married to complete a step parent adoption or adult adoptions may not be allowed.

I agree that the first order of business here is the mother. Unless your son is married to her, she has the say over how the child is named. So even if your son does change his name, she doesn't have to go along.

Even if they are married, she may have to agree to legally change her name.
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Good point. Scott is referring to the mother of OP's expected grand-child.

It should also be noted that, depending on the state or country, the surname of the baby (as shown on the birth certificate) might be at the option of the baby's parents. Thus, for example, if OP's surname is "Adams", her boyfriend's surname is "Baker", OP's son's surname is "Cabot", and the baby's mother's surname is "Drake", the baby could be given any of those surnames, or any other surname for that matter (again, depending on the law if the jurisdiction).