TJ he was 13 weeks old and Roxy was 6 months old when I got them. TJ was the 'overly excited pup' while Roxy was VERY scared and shy and timid. I remember carrying her outside in our backyard, she was 'shaking' nonstop and she kept her face glued into my neck. TJ was just looking all around in excitement.
I don't know for sure 'what' kind of life they both had at the breeder, but obviously Roxy wasn't given the proper socialization, that's all I can think of.
When we would all sit on the couch, there was TJ crawling all over us, and poor Roxy was at the farthest spot possible on the couch with her face buried in the pillows. After a few months, she would lie on my ankles, then after a few more months, she would lie on my tummy and then after more months she would plant herself on my chest. It has been 2.5 years now and she has come a long, long way. She is not a face to face dog, she doesn't like 'loving' - don't get me wrong she wants to be with me all the time, but on her terms. She won't play with me either, but I do catch her playing by herself and sometimes with TJ.
It takes a lot of time, patience and love. There are a handful of books that you get can about Shy Dogs - How to Help Shy Dogs. One thing I learned was to build their confidence. You can do this by teaching commands. I can't get Roxy to focus to learn 'tricks' b/c all she wants is the treat. But I did teach her to "Give Mommy a Kiss". She won't really touch my mouth, but she comes in real close, real quick and then backs away. Well, that's good enough me for