It is a matter of tradition, culture or religion. I have gone to a Jewish wedding and the bride's mother and father walked the bride down the aisle and stood at her side the entire ceremony. Other weddings that I have gone to I have seen the bride's parent's sitting in the front row.
Usually in Christian ceremonies, the Mother of the bride is escorted down the aisle last by an usher ...right before the wedding party starts and is seated in the first or second pew. Second pew if the bridal party is using a pew...first if not. The father of the bride will escort the Bride down the aisle and then be seated next to the Mom....Now there are many variations on this under different circumstances, divorces, step parents etc....Hope this anwsers your question
