They're both sober and going to meetings, what's the problem?
It has been said that men often mistake the limits of their field of vision for the limits of possibility. This is ever so clear in AA where 90% of the folks you meet seem to firmly believe that they have the monopoly on staying sober and having a good life and nobody could possibly have the same results without doing precisely whatever it is they're doing. This is simple, juvinile, egocentric, and possibly narcicistic. to the extreme.
How about try some attraction rather than promotion. If your step meeting is in the meeting schedule and what you are doing seems appealing he will probably investigate it with or without his sponsor.
How about instead of condescending rubbish like "when are you going to get into the work" or "how quick do you want to feel better?", you treat AA like a fellowship (a gathering of equals) and say things like "you're doing great!", "aren't you glad you didn't wake up hung over today?", or "hey, we're going out for coffee after the meeting and would love to have you come along". (Not implying you're doing one and not the other, just throwing out the kind of ego feeding that helps nobody vs. encouragement, attraction, and inclusion).