HI, I can understand your concern for getting thick eyebrows. The eyebrows hair are basically genetically mediated so it depends on family pattern. It can not be grown by applying any medicine or any home remedy products like garlic. You should not apply garlic over the eyebrow area as it can cause severe contact irritant dermatitis and problem in eyes too. It can burn your skin and cause pigmentation on healing which can be really bad. You can take vitamins in the form of biotin, calicium pantothenate and other vitamin B complexes. Additionally increase you protein intake on daily basis and eat sprouts. Eat a lot of green leafy vegetables and sprouts which contains vitamins and minerals necessary for normal hair function. You should consult a dermatologist and take guidance. Take care.