Why so snarky Crafty? OP has explained her family situation, how close her DS and his step dad are is nothing to do with this issue 
I know how you feel OP, you just want to know that he’s on the same page, but not everyone sees the value in marriage.
My DP isn’t fussed either way, he doesn’t see it as something important, but he’s also happy to get into sharing property etc so it’s not a lack of commitment. He had his DCs with his ex without being married, so it just isn’t something that he feels the need to do.
For me, it is important, it’s a public statement about your commitment that makes others treat you differently. At the moment I am very much “just his GF” (and as Crafty has shown above, some people on here and in real life are quick to dismiss you whenever you don’t have the official title of wife, son, partner etc - how many times have we read “so he’s not your partner, he’s just a boyfriend” or “you’re not their step mum, just their dad’s girlfriend”).
I waited for ages thinking he would ask while we were away for the weekend or on an anniversary etc (again, we’re not allowed an actual anniversary according to MN because we’re not married, so the date we met and celebrate is irrelevant!)
We have discussed marriage and he’s agreed that he’d like to do it in future as he knows it’s important to me, but we never got any further really.
In the end we were talking about money one day and I said “shall we put aside a bit for a wedding too?” He said “sure” and then made a joke that I’d just proposed to him and he’d tell everyone that I’d got down on one knee etc
We since split up and got back together so I don’t know if it still stands! I guess now I will have to broach it again, but I’m not going to torture myself by waiting for a big romantic gesture which may never come.
I’m not at all traditional and find the patriarchal traditions surrounding marriage a bit jarring, but I do want to know that he’s as into the idea as I am before we actually do it. I think the wedding itself is the big romantic gesture. Deciding to do it should be a mutual discussion about when, why and how you want to do it.