Is there any medicine in homeopathy that can help me grow taller at the age of 20? I'm- 5`4, dad-5'6, mom-5 feet.

Accept it. Homeopathy is my favorite treatment but it has limits. I am sorry to tell you that most men stop growing by age 18 (though occasionally there will be slight increases up to about 21). But no 20 year old is going to grow much more. Once the growth plates of your bones have closed further growth is impossible. At this point all you can do is accept that this is who you are and how tall you will be.