Have you ever read that passage where MAry and Jesus’s brothers AND sisters stood outside a house and asked to speak with Him?
Yes, a thousand times and the first time I read it I thought as you do, that mary had other children.
Jesus had brothers and sisters is the only hint that mary had other children which is a false concept.
There is no hint other than that that mary had other children
but there are several scriptures that hints pretty strongly that she didn’t.
John 19:25-27 25 Near the cross of Jesus stood his mother, his mother’s sister, Mary the wife of Clopas, and Mary Magdalene. 26 When Jesus saw his mother there, and the disciple whom he loved standing nearby, he said to her, “Woman, here is your son,” 27 and to the disciple, “Here is your mother.” From that time on, this disciple took her into his home.
The above scripture alone is enough to convince any one that Jesus was Marry`s only child.
not to mention the other scriptures I gave you.