To clarify: we had many opportunities in the past to get to know each other better... He was in my class for three years, we worked on some group projects together, I grouped with him some times for practical classes. I called him an aquitance and he was one of the classmates I would talk more with...

And don't even know if it is going to happen, I don't want to say no, but I find excuses to not to do it, and don't make an effort to find a convinient time. I just want to do it without my sister to know for not a much racional reason. And what does this makes him think of me? Is strange how I can't make sense of my emotions, many of my reasons aren't racional and I don't know what to make of them.