How to talk to my brother about his stutter?

How to talk to my brother about his stutter? So some context: my brother is several years younger than me and has always had a moderate to severe stutter. I’ve always been supportive of him and I help when I can (I only see him about twice a year at this point), but we’ve never had an actual conversation about it. I just want to reach out to him to ask how he’s doing and if he’s considered going back to speech therapy as he only went a couple years as a child. I know that stuttering is a daily lifelong challenge especially for a new high-schooler so I want him to know that he has support, just not sure how to approach it. Should I wait until I see him in person and bring it up casually or should I reach out sooner?