jamaica

Me and my partner have been together for almost 6 years and been living together for 5, i have a 6 yr old son that he has raise for all this time .
He is from jamaica and has over stayed for many years, he has never been in trouble with the police or anything like that. Mine and his family has help him so he has not had to work or brake the law in any way,
We now would love to get married and have more children and he so longs to work, but know for this to happen he will have to return to jamaica, my fears are that he will not be allowed back to the uk for 10 years,
What i am asking is if he dose go back to jamaica will they let him back to the uk and how do we go about it as i am not sure on the rules of the immigration
Thanks for advice you way be able to give
Emma