On 6x6 wondering about Sayid and his brother with Nadia

How can his brother be with Nadia, if in season 5 Nadia was with Sayid after he escaped on the helicopter. Were they not together romantically during that time? Where was his brother at that time? Or do I just need to keep watching to understand it? No spoilers for the rest of the final season please and thank you. I feel similar about this as I do to Jack's kid. Is this like a season 6 thing, where there are just major parts of the character's lives that we didn't know about before?