Stavros Cassadine kidnapped Lulu and then froze her (Coles notes version of the story!!). Because of the freezing, she only had two good eggs left in her basket, so to speak. The eggs were retreived (I forget how or why), then stolen. Dr Obrecht had one egg, which she fertilized and implanted into Britt. (Britt then pretended Patrick was the baby daddy). After Ben was born, LIz found out that he was Lante's baby and spilled the beans to Nik, who was dating Britt at the time. Ben was given back to Lante and renamed Rocco.
Embryo number two was taken by Helena and fertilized by Valentin. Valentin took the embryo and implanted it in surrogate Claudette. Claudette took off with baby Charlotte, then pretended Nathan than Griffin were her baby daddy. Until Valentin showed up and said he was the baby daddy. Lulu figured out that Charlotte was hers and so she is.
I think it's deliberate that Sasha looks so much like Britt. She's supposed to be Nina's daughter. Nina is Dr Obrecht's neice. Britt is Obrecht's daughter and Nina's cousin, so it would make sense that Nina's daughter looks like her cousin. The weird thing is that Valentin hired Sasha to pretend to be NIna's daughter, so the question is, is she supposed to look like Britt because there really is a connection there, or is it just going to end up being a coicidence.
Yep. though the guy who runs it, Shiloh, claims it's just a group of people who do charitable work in town.