How it is possible that Sanskrit is related with Greek and Latin?

These are all in the Indo-European language family, but they diverged from one another very early on. In fact, Hellenic (Greek) and Indo-Aryan (which gave rise to Sanskrit) were among the first major branches in the Indo-European tree. Italic came not long after, and led to Latin and Italian. Because these divisions happened early, there are large differences between the languages (particularly Sanskrit vs. Greek and Latin). Only a linguist would see similarities.