It was said that Sam is 26 and he was conceived before Bree and Rex met, but he would have to be older if that were the case. In season 1, it was stated that Bree and Rex had been married for 18 years, but it's been 10 years since then, which means if Rex were still alive, they'd now be married for 28 years, and Sam would have to be at least 29 or 30 for him to have been conceived before Rex met Bree.