If I add my brother to the deed via a quitclaim deed and the Masschusetts transfer tax is nominal then would I have to pay a gift tax

It is unlikely that you will have to pay any actual gift taxes because of this action, but you will almost certainly have to file a federal Form 709 (Gift and Estate Tax Return).  Massachusetts has no state-level gift tax reporting or form required, so there is no obligation to file such tax forms to the state (except any transfer tax on the real estate deed, which is an entirely separate issue).  But there is a federal gift reporting obligation.

That said, you should find what you need to know about Form 709 and gift taxes by reading the following detailed AnswerXchange post and discussion:

https://ttlc.intuit.com/questions/3878767-joint-tenancy-and-gift-tax-question

Those same basic principles (and the $14,000 annual gift exclusion described there) will be directly applicable to your own situation, at least with respect to the transfer of property ownership interest from one brother to another.

Please know that Form 709 is not available in any version of TurboTax, and that you would either need to fill out (and file) this form manually yourself; or you would need to hire a professional local tax preparer to do it for you.

Thank you for asking this question.