Not collusion IMO.
The 4-6 team is not out of the playoffs. They still have a chance to finish 8-6, and depending on the other records in the league, mathematically speaking, I assume he's still in it. Ignore the fact that they are brothers, and ignore the team's records and look at what the trade does for each team. It would be helpful to see the complete rosters of both teams as well, as the context is really the only way to tell if the trade is fair or not. Looking at the players in a vacuum is not a good way to look at things.
Drew Brees > Peyton Manning
Witten < Graham
After that, it's hard to determine Ray Rice vs Andre Johnson. In a vacuum, Rice is probably more valuable, but what other players are on each team? If the Ray Rice owner is stacked at RB, but has no WR, he'd make this trade in a heartbeat. The reverse is true for the Johnson owner if he's stocked at WR. I don't think the trade is that lopsided really, and you can't fault a player for improving him team via trade...that is the whole point of trading!