Twelve people, including two children are being assisted by the Red Cross following a fire in their 2-story, 4-family apartment building in West Allis this morning.   According to the West Allis Fire Department, the fire was discovered around 6:30 a.m. Saturday in the basement of the structure at S 88th and W Mitchell Streets.   The fire extended through the walls to the first and second floors of the building.  One adult resident was taken to the hospital suffering from smoke inhalation.  There is no word on the victim’s condition.  There were no other injuries.   Firefighters from West Allis, Milwaukee and Wauwatosa were on scene for about two hours battling the blaze.   The Brookfield Fire Department also assisted.   The cause of the fire is currently under investigation and there is no estimate of the dollar amount of damage to the apartment building.