Should you sit next to him when meeting his friends?

Before you sit anywhere, look at how the group is already arranged. If his friends have drifted into their usual spots and he's standing at the end of the bench, the seat next to him might be the natural one, and taking it just makes you part of the setup. If there's an open spot across from two of his friends who are already deep in a conversation, that's a chance to join them without competing for his attention.

Also notice how he behaves when you walk in. If he moves over to make room and introduces you warmly, he's already placed you somewhere and sitting near him matches what he wants. If he gives you a quick hello and turns back to whoever he was talking to, don't read that as a rejection, but do consider that he may not have framed you to the group yet. In that case, a seat slightly apart lets you settle in without forcing a label.

The point of the first meeting is to get a feel for his friends and let them get a feel for you. Pick the seat that puts you within easy talking distance of the most people, even if that means one seat away from him. Sitting at the corner of a table or at the end of a booth usually gives you eye contact with everyone and a natural way to turn toward whoever is speaking.

If you do end up next to him, use the seat to include others rather than to draw him away from them. Turn your shoulders toward the rest of the table, ask the person across about their job or the thing they just mentioned, and let him join in. The friends will remember whether you were a good conversation to be part of, and that tends to matter more than where your chair was.

Seating is not fixed once you sit down. If you started across the table and the conversation has settled into a rhythm you want to join, move when there's a natural break, like someone going to the bar or a round of drinks arriving. You can say something simple like I'm going to grab the seat by the window before someone takes it, and that gives everyone a reason to shuffle without making a thing of it.

If you started next to him and it feels too close, the same logic works in reverse. Lean back, shift your chair, or ask the person beside you a question that pulls your attention outward. You don't owe anyone a perfect layout. The goal is for you to be relaxed enough to be yourself, and that is usually visible from across the table.