Yay! I finally finished the four is enough, twins, and no vacancy trophies. I just gave my mother (Odessa) a baby boost and whenever she and her husband (Bingur) tried to have a child, they did! Here's my family after the baby boost:
Odessa (mother)
Bingur (father)
Bistro- in college
Ponto- 18
Artetto- 16
Otto- 13
Chaka and Inky (twins and only girls to be born of Odessa and Bingur)- 6

I'm going to use either Chaka or Inky in the next generation, because they have purple hair and I really want to experiment with that.