In Sonnet 133, male friendship is a huge deal for our speaker. It's far more important to him than any romance he might have with a woman. Even though one of our speaker's BFF's is totally hooking up with his mistress, guess who gets blamed? That's right—the mistress. Our speaker doesn't blame his buddy at all, and instead portrays the friend as an innocent victim who's being tortured by a cruel and sadistic woman. At one point, he even offers to sacrifice himself to his mistress just so she'll stop torturing his pal. So what gives? Well, part of it has to do with how close the speaker feels to his beloved friend. In this sonnet, he famously calls the guy his "next self" (a.k.a. his other self, or his second half). That means that, when his friend suffers, he suffers.
Truth be told, that doesn't really surprise us. Male friendship was a big, big deal in Shakespeare's day. (Go read about the bromance in The Merchant of Venice if you don't believe us.) It was considered the most important kind of relationship a man could have (even more important than his relationship with his wife). Oh, yeah. You should also know that the speaker addresses all of Sonnets #1-126 to this same buddy and spends a ton of time in Sonnets #1-54 trying to convince this guy to go out and have babies.
The speaker calls his friend his "next self" (6) because he identifies with him and because the two men are so close that our speaker feels like he can literally feel his buddy's pain. Ouch.
Fellas first. Male friendship is more important to our speaker than his romantic relationship with his mistress.