I wouldnt consider the other relationships as comparators, you said yourself that your friend had a long-term girlfriend!
I'm 25 so I appreciate that it's not the same situation with children etc, but I would be quite freaked out if I had a proposal after two years, or if someone had the 'where are we going' conversation.
You love this guy, and just as important is the fact that your boy does - don't scare him off with this stuff. It might be that two years just isnt long enough for him to consider the commitment.