Discount brokerages require a minimum age of 18. However, you can create a sub-account under your dads name (as long as he signs some sort of consent form) and these sub-accounts don't have a minimum age requirement.
Vitamin D deficiency rickets can be caused by a lack of vitamin D in the diet, a lack of exposure to the sun, or malabsorption syndromes in which there is an inability of the intestines to adequately absorb nutrients from foods.
The classic symptoms of vitamin D deficiency is rickets in children and osteomalacia in adults. Rickets can cause skeletal deformities, such as thickened wrists and ankles. It can also cause muscle weakness and pain in the back, pelvis and legs.