Sure, that's new but not surprising. I don't think he'll be here beyond his contract though, it's rare for siblings to all make the bigs, let alone a sibling trio. What actually happens is anyone's guess but I'm expecting Luke to successfully make the jump and I do think Quinn will look to join them at some point in his career. An NHL career doesn't last forever, to play as teammates with your siblings would be something special.
EP's expressed interest in extending long-term but I think his contract will likely come post-Matthews signing. That signing will raise deals around the league imo. I'm more inclined to believe he sticks around regardless of what we do going forward, but they've shown him a willingness to at least try and be competitive.