@blueminds What is the relevance of your 'poor' backgrounds? You mention is twice.
Are you trying to say that on your own, without him, and vice versa, you could not be where you are today? Did you cling to each other as a mutual support 'agency' to get through uni and build a family BUT you are more like friends than lovers?
Otherwise I don't see the relevance of your poor backgrounds. Lots of couples have poor backgrounds.
Presumably when you had kids you thought your relationship was for life. How old are they ?
Was there a reason why you had kids first but didn't marry?
Were you unsure and thought the kids would 'bond you'?
Why is marriage important now?
I am always a bit
at couples who say they are engaged when they already have kids because they have already made a huge, lifelong commitment by having those kids together.
In your case I can't see how being married or not married makes any difference other than the financial security it would give you as a spouse.
It's really too late to start wondering if he's not right for you as you have made a huge commitment by having kids. They deserve you to dig your heels in and find a way through this.
Walking away at the first sign of 'boredom' or whatever isn't the way to go.
I've been married over 30 years and marriages or long relationships go through boring stages. Unless you feel he and you are completely incompatible, or he's aggressive or abusive, or totally selfish, you should try to make this work.