Its only a problem if you make it one i think
My ex husband was 15 yrs older than me (although mentally im convinced he was a lot younger than me!!) That obviously didnt work but the age gap never really was an issue to me.
My current fella is 7 yrs older which isnt much but isnt an issue
Must admit though, when i was 15 and my fella was 19 that did seem like an issue to many. The relationship did last for 7 yrs but i grew up, he didnt
I know of a few relationships where there is a large age gap, one is a 30 yr age gap but that is no problem to them and shouldnt be to others.
So long as your happy it makes no difference how old you both are