That wasn't the subject of the verses quoted.
Dr. Eckleburg quoted them in response to Marlowe's statement "There is no scriptural basis for the contention that Mary was born without original sin. There are plenty of verses to the contrary" (3212). Apparently Dr. Eckleburg thinks that the verses indicating that Mary had a large extended family somehow point to her sinning. These verses may be interpreted as Mary being mother of other children beside Jesus, but for the life of me I do not understand where they point to any sin in her.