Depends upon the situation.if bride is 12 years older than bridegroom then it is completely unacceptable.on the other hand if bridegroom is 12 years or even in some cases 20 years old than bride,marriage is acceptable.
Our society is mascuiline centered.If unable to secure marriage before 30 years of age,Girls are seen as defective.I know a 32 years old ladywho is highly intelligent ,educated and beautiful but she didnot get marriage proposals due to her age.she is one of my acquaintances.