Hair Loss Genetics

Hey everyone, I am new to these forums and I bet this question has been asked quite a few times already, but I am really too impatient to search for it elsewhere.

Anyways, my question/concern is: I am worried about losing my hair/going bald. My father and his father were both bald, however, my mother's side of the family(my mother's brothers and father) had full heads of hair with no hair loss.  I have an older brother who is 25 years old who has not lost any hair (maybe a very little bit near the temple area). I am 19 years of age (male) and like my brother, I am noticing slight thinning near my temple area as well.  Everyone who I've asked has said I have nothing to worry about and that I am NOT losing hair. However, I'd like a more qualified opinion.  So, in short: am I at risk? Is the slight thinning of my hair near my temples normal? Does a slight thinning in that area indicate a good chance of baldness?

Extra information: My father had lost most of his hair at about the age of 19-20.  Also, my brother has straight hair where mine is naturally curly/wavy.

Thanks a lot!