The reality is that your boyfriend’s relationship with his sons will always be older and deeper than his relationship with you. Kids, being kids, are going to need his attention in ways I hope you don’t. He can’t love you “as much.” He can, and should, love you differently — and deeply. Partner love is very different from parenting love. There is no competition. They are entirely different emotions. There is no “number 1” when it comes to love in a family.
“Getting over” your thoughts is a decision. If you can’t make that decision and stick to it, you owe it to this fine man, the kids, and yourself, to take a big step back from the relationship. It may be that the age gap is more of a problem for you than you are willing to admit. It may be that on some level you know you aren’t yet mature enough to take a parenting role with two children who are going to need you to do just that. It may be that as much as you love him, you don’t really want kids but don’t want to give up on the man — even though it is absolutely a package deal. Or it may be that you aren’t yet secure enough in your own adulthood not to be jealous of what children rightfully get from a parent.
It would be wonderful if I had a way to help you grow into being ready to be a partner to this man and a stepmom to his children. Unfortunately, I don’t. I hope you will work on it. If you can’t get to a better place, I hope you will be fair to everyone — including yourself.
I wish you well,