Hi,
My friend, Dogbreeder, gave you, as she always does, an excellent answer (gave her 2 thumbs up). I believe that you raise the point not because you know him only for a short period but because he is some 5 years younger than you are. If it's only the age gap that bothers you, better ignore it.... Maturity is more important than age. Ask yourself: If he was 30 tears old, would I marry him ? (Do I really love him ? Is he a good friend ?, Will he be a good husband and father ? Is he a serious steady person ? Do I love being with him ? etc) - if the answer is yes, go for it.... if the answer is no, better wait..... Ignore the age gap..... As Dogbreeder wrote: the most important thing is to know him well. That is 100% true.
Best regards,