Aramis’s chief function in the novel, plot-wise, seems to be his status as the lover of a certain Madame de Chevreuse. When not driving the plot forward, Aramis’s story line adds a bit of comic relief. He and Porthos are later important in serving as witnesses at Milady’s trial.
Even more so than Aramis, Porthos functions as comic relief due to his supposed exploits and incessant bragging. Still, he is a loyal and strong friend, and he and Aramis are later important in serving as witnesses at Milady’s trial.