My Theory after watching episode 9 on who is the last living descendent.

Guys, sorry for the spoiler, but i have a theory and its pretty accurate:

Ruth had a child and its Lauren, Evan's Mom.

Clue No 1. Ruth was so easy about babysitting Evan for all those years. I guess she just wanted to spend time with her grandson.
Clue No 2. Everyone has two mothers,” per Lauren’s letters to Evan, hinting that ruth gave her baby for adoption i guess.
Clue no 3(important). Remember in the flashbacks in the starting of episode 9, One child on the boat said “I can’t see!” ,, we also heard that from Lauren, Evans mom, on the ferry… both were in the verge of leaving the waters, so once they come near the boundary they may suddenly loose the eyesight. Also remember the Hortence whore who followed Loftis, she had also lost the sense of eyesight we know that she is also the descendent of Richard warren.

So i think, Lauren is the child of RUTH and Evan is the last Living Descendent.