Mary White's father (or Mary's father) is the only mentioned parent of Mary White. In Fuuko's bond event, he was mentioned in her history of when she entered a tornament against Izzy. He watched Izzy and Fuuko in the tornament before later passing on.
Although his appearance remains unknown, it's likely that he shares a simiar appearance to Mary. Mary appears to have white hair-so there's a chance that he did too.
Not much is known about him, other than him being the father of Izzy. He was struck down by an unknown illness but regardless visited his daughter on the day of the tournament against Fuuko. Izzy lost and her father shortly passed away afterwards, and Fuuko-overhearing Izzy crying and blaming the loss of the tournament of it being herself-Fuuko felt responsible for her fathers passing and blamed it all on herself.
It also remains unknown how this illness begun, such as: if Mary's father had always had it or if it was recent.