front vibrates when I apply the brakes

if your car vibrates when brakesare applied it is probably warped rotors. they warp due to heat from hard stops or not being turned. A lot of todays rotors are also thin so they can't take theheat like the older ones do so they warp. It cold be a front end problem as well and should be checked out. Normally a brake job willtake care of the warpage problem though

should this happen after only two years? thanks

yes it can, it really dependson what type of brake pads andthe way vehicle is driven . Like you said you have 25,000 miles on it since and if it is more city /suburbia driven then this is more likely.