HuffPost: You write that Bristol wanted to get pregnant.
Johnston: Bristol was on birth control for a long time. She got off it soon after Trig
was born. I think Trig was a big motivator for her. Her mother just had a child and I think Bristol was really jealous. She was the one who was supposed to have that kid and that's when she got off of . We weren't practicing safe sex and she ended up getting pregnant.
HuffPost: What do you mean she was the one meant to have it?
Johnston: We'd always talked about a kid. We'd been dating for several years. I think it kind of hurt her because she really wanted a kid so bad and seeing her mom have another one really made her want a kid now.
HuffPost: You say that Sarah kept Trig's pregnancy a secret until the seventh month.
Johnston: Yes, she kept it very secret. Willow had actually found the pregnancy stick in her bedroom. That's when we all found out because she went around telling everybody. Bristol and the whole family was hurt that their mother couldn't share that with them. Keeping it away from your own family is kind of messed up.
HuffPost: Describe Sarah and Todd's marriage.
Johnston: I'm no marriage counselor here but I had a mother and father growing up my whole life. (The Palins) were completely, 100 percent different from my family. They rarely spoke to each other, they never had family meals. I never saw them really do anything together unless the cameras were on and then they played an American family. Todd always slept on the couch, never in Sarah's room, that I've seen.
http://www.huffingtonpost.com/2011/09/21/levi-johnston-bristol-palin-book_n_973465.html