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Masturbation doesn't have any effect on growth. You could masturbate all the time, or never at all, and you will be the same height.

Your height is determined by genetics, and to a lesser extent, nutrition. Although unless you are malnourished, what you eat isn't going to affect your height much either. But you should eat a healthy, balanced diet, and get plenty of rest.

The gene that determines height can vary among siblings. So just because your brother was taller at 14 than you are now doesn't mean that you need to be the same height. Also the rate and order of puberty can vary among siblings. So you may go through your growth spurt sooner or later than your brother did. You could end up taller or shorter than your brother when finished with puberty - there's no way to know.