Your inquiry touches a little known early Sewall family of Massachusetts. Their tracks are few but suggest the following story.
There was a Thomas Sewall in Springfield in 1650. He may have been the same Thomas Sewall who was seen in Boston in 1652 and 1656, and the same as the Thomas Sewall was seen at Chelmsford in 1659. The chronology allows these to be appearances of the same man, but they could have been two or three different men as well.
Thomas Sewall of Springfield may have had a daughter in 1649, but the child could have belonged to a Thomas Lowell instead. At any rate the child was dead within weeks. Thomas Sewall of Springfield did have a daughter Abigail born in early 1650. I have not seen any record with the name of Thomas Sewall's wife.
Thomas's daughter Abigail is said to have been the second wife of Alexander Phenix, though on what basis this claim is made I do not know. Alexander Phenix is said to have come from Scotland to New Amsterdam in 1643, to have been at Kingston, R.I., in 1652, and at Wickford, R.I., in 1674, and to have died by 1687. He did have a wife named Abigail, and if she was Abigail Sewall, as is said, she was much younger than he. She may be the Abigail Phenix who purchased land at Kingston in 1709, and she is said to have been still alive in 1717.
Thomas and Abigail Phenix had a daughter Abigail, who married Benaiah Brown about 1683. Note that if Abigail Sewall, born in 1650, was her mother, either or both mother and daughter were in their teens when they were married, as there is only 33 years between the mother's birth and the daughter's marriage.
Benaiah Brown may have been the man of that name born at Rowley, Mass., in 1648, and at any rate, he died at Kingston in 1717. I understand Benaiah and Abigail had children, but have not followed this line further.
There is no connection between Thomas Sewall of Massachusetts (be he one, two or three men) and the family of Judge Samuel Sewall of Boston. Abigail, the daughter of Thomas Sewall of Springfield, was born two years before Judge Samuel Sewall.
Do let me know of there are more questions. Best wishes,