The description for Doris on Moshi Monsters does not say if Doris is male or female, so you can decide for yourself if you want your Doris moshling to be a boy or a girl. Doris is usually a girl's name, so many Moshi Monsters players choose to have Doris be a girl.
When Doris Day was eleven, her father separated from her mother and later divorced. Of course, Doris was aware of the divorce. Doris described in her biography Doris Day, Her Own Story by A. E. Hotchner that her father's "leaving was an enormous loss to me."