Disappointing facial hair growth is an issue for many men. Genetics are the most important factor and determine almost completely the length, thickness and color of facial hair you can grow. For a mustache that has two thick sides but doesn't connect in the middle, use of some simple grooming tricks may help your mustache appear as though it connects naturally.
Use a small, fine-toothed beard and mustache comb to manipulate the hair you can grow. Comb the hair in different directions to see where it goes most naturally.
Dye your mustache hair to a darker color. The hair in the middle of your lip often grows in less thick and in a lighter color than the rest of your mustache. Dying the blonder hairs darker will help your mustache appear as though it's connected. There are many safe commercial products, such as Just for Men, made for this purpose.
Maintain your overall health diligently. Eat whole foods and a protein rich diet, sleep at least eight hours every night and take vitamins for hair growth. Vitamins that promote hair health and growth include biotin, vitamin B6, C and E. Consult your physician before making dramatic changes or additions to your diet.