There is no best age to get married. It can be the early 20s or late 30s. If the person has established oneself and feels like one should share the life with another individual, one should go for it. Getting married at a certain age is nothing but societal pressure, and that is why this question about age pops up more often. But, ideally, it should be the maturity or readiness of the individual that matters the most.
Marriage means lot of responsibilities and you are ready for marriage only when you think you are capable of shouldering the responsibilities. And it does not matter if you are in your 20s , 30s or 40s. No one can tell you at what age should you get married. It is you who will decide.