strange behave

i write in english because my good friend dont know hebrew. I"m married , , my friend is married too he is 59 years old.I wanted know if his behave is normal for a adult man.He is unhappy in his marriage, His wife have all the control at home, in shortly. he is aftraid from here ,he never say his mind she deside al alone,and he just follow, do all what she say).With me he talk only about one subject ----SEX---asking many strange question about it,thats all what its interesting him when we talk. My question is:: is that a normal behave for a man that is married 35 years ? I have a feeling that i am some kind of psycholog for him.I have to answer on all that strange sEX question. What can be his problem that he like talking mostly about this subject? Pls would like a explenation what can be his prob. thank oyu forward LISI