A portmanteau is where two or more words are combined to make a new word (e.g. bootylicious, turducken).
A portmantbro is a portmanteau where one of combined words is "bro" (e.g. brogrammer, broga, humphrey brogart, broadkill, etc).
Me: I tried going to broga for the first time yesterday, turns out it was a bunch of brogrammers. I was totally broadkill.
Grandma: Can you go a single sentence without using a portmantbro?
Me: Chillax Humphrey Brogart.