Not being able to show love to parents and sister

**There is something I'm not able to overcome in my life. **

I'm not able to show my love/affection to my father, mother and sister. I mean, I love them but I just can't get what's inside me out for them. It's not that they didn't show me any love or something like that. It is the opposite. They never withheld their love for me. I always felt it with their words, behaviors and body languages. I always felt their love.

Yet, I always felt guilty that I was not able to show the same emotions to them. Even when they say "I love you" to me, it is really, really difficult for me to say that back to them and I don't fucking know the reason. Most of the time I answer them back with something like "thanks" with a smile in a shy way.

I can pretty much show my love to wife and cat without any problem. So I believe that I just can't show it to the people I'm related to by blood. By the way, my family knows that I love them. But I also feel that they would be happier If I could show them the love in a visible way like they do for me.

Well, as I was like this since my childhood and considering that I'm married and 27 years-old today, it is much more difficult for me to change, I guess.

Though, I have been feeling that I'm getting emotional as getting older. Maybe I can break the ice in my heart and one day I can freely tell them that I love them.