Sayid: Nadia or Shannon

Can someone explain this to me. Sayid is searching for Nadia because shes the love of his life. He almost finds her but flight 815 crashes and puts that on hold. He then gets all cozy w/ Shannon and becomes whipped. I cant remember if they say they love each other, but regardless, Shannon dies. Sayid then gets off the island, finds Nadia, and marries her. She then dies. So what is up with Sayid and Shannon hooking up in the afterlife? Shouldn’t it have been Sayid and Nadia? And who the heck are these kids Nadia had w/ Sayids brother? I’m so confused.