Bartlett. *** POSSIBLE SPOILER***

Is Bartlett Euphemias brother in law or uncle. At the beginning, when Phemie finds out her father has died, Georgia tells her that her uncle Bartlett is coming to get her. But through the rest of the movie, it shows that Bartlett is married to Phemies sister. How does that work? Also, why is Sarah looking after Phemies brother, but not her. They look fairly close in age.