Hi,
i think that while dating you parents are only looking out for you best intresets (most!) and if they had a reason to be concerned then they feel obliged to do so, for you sake.
However, some parents mightnt like the 'look' of somebody and prejudge them. I know from where i am from my parents didnt like the 'look' of anybody and therefore i got the vibe they didnt approve. But if they dont approve, there is plenty of time for your partner/date to change their perspective of them.
But i think it really all falls down to what you think. Its you who is dating the person anyway, not them.
If your mum is negative towards you a lot of the time then you have to accept that she is not doing any good for you mental health. Please reconigise her words/actions for what they are and then do not let them effect you (much easier said then done, i know)...
"its is not events or situations that make us happy or sad, it is how we react that determines how we feel"
....please keep that quote close in you mind okay? Because, to have a parent that fills us with megativity, unconciously they can pass this on to you. I had to keep this quote on the top of my mind as the negativity in my home was awful. But on another note, you are lucky to have caring parents, and as previously mentiond they are looking out for you. They do not want you to end up with somebody who is not good for you.
Maybe listen to what they are saying, take there points onboard, and if you still disagree with them, then there is nothing more they can really do. The choice is yours, not their's.
You said he is 12 years older than you. Age is only a number. I went seeing somebody who was 10years older than me (i was 20), and i seen somebody who was 15 years older than me. And soon im going on a date with somebody who is nearly 10years older than me. Thankfully becoz i was a troubled teenager my parents my parents were afriad to say anything to me incase i kicked up fuss but i could tell they were a lil bit weary of the men. But as they soon got to know him there opinions changed and grew fond of him.
If your parents firstly dont accept him, allow them some time. I understand their opinions matter but you opinion matters first to you. Dont do anything too drastic just yet, allow time for them not to judge him on his age. This is all my opinion, obvisully i dont know what you feel is best, but i think time can tell for you
Why do you think they disapprove? The age?