Dragon Age 2 Spoilers?

Do you want to know some spoilers? if not, leave the page. I went into the deep roads with my sister (Bethany) but she dies at the end, if i dont take her she goes to the circle. Is there anyway to keep her? The same thing happens to your brother (Carver) though either you take him and he dies or he goes to the templars. With who can you have a relationship with? i know you can with Anders, Fenris, Merrill, The Pirate Chick can you with Verrik or Aveline?