If Brad and Robbie's relationship went under because he was messing around with Matt, I wonder who the family would side with. Brad may be JP's de-facto "successor" and have all this influence, but by their family's standards I'm pretty sure this crosses the line. Matt would, ironically, be the "brian" or more approriately the "Jake" who screws up established relationships. I'm sure his siblings would think of him like that, but I don't if the older generations would shun him or not. Either way this is all idle speculation that's making me even more curious about how this will be worked out!
EDIT: Chap 4. was interesting. I almost forgot how slutty Matt and Wade are. If Brad were to have sex with Matt now, I think the family would be divided over whose corner to be at. If Robbie and Brad were to reconcile before Brad slept with him, it would be even more devastating and more people would be on Robbie's corner.
I'm starting to have conflicting feelings about Matt. I know he's a horndog, and he's pissed at Robbie, but wouldn't he be more loyal? He's only a Hayes by blood, but I thought he's have more conflict over having sex with his dad's partner. Again, if you do this, I hope it's more than a one-night stand.