Twins raised together and twins raised apart

#1
Greetings All,

I am examining smoking behavior in a sample of twins raised apart and together.I have repeated measures at different time points asking participants if they smoke or not. I also have a question about whether the participant grew up in a household where parents smoked.

My research question is whether smoking in the household has an influence on smoking behavior. I hope to make use of the twins raised apart and use the twins raised together. For example, if Twin A and Twin B were raised apart; Twin A experienced smoking in the household but Twin B did not. I hypothesize that Twin A is more likely to smoke than Twin B. However, I have not found any documentation or models that would allow me to answer this question and unfortunately none of my advisers were sure how to do this either. My idea is that I would want to use fixed effects to "erase" the effects of genetics. But I'm not sure if this makes sense because the twins raised together may also have fixed family environment. I'm also wondering if the twins raised apart would constitute random effects.

Alternatively, I am looking to examine if different parental behaviors have an affect on later life smoking behavior. In this case I would like at associations and not use a survival model.

Any feedback or suggestions are much appreciated.