A wide forehead sizes is a virtue of genetics. Hair growth starts from the scalp line irrespective of the size of the forehead. Hair cannot be grown on the skin of the forehead. If the hairline on the scalp is receding you can use lotions and procedures like mesotherapy and platelet rich plasma injections for hair growth.
There are different types of hair fall and thinning, and understanding which type you might be experiencing is the most important step towards getting it treated. Androgenetic alopecia (or pattern baldness) has a large genetic component, while telogen effluvium is usually a response to an external factor (like stress or illness).