It gives me serious doubts about going into academia.
Let me try to put your mind at ease about this by first of all answering a slightly different question from the one you asked: it is very, very, very normal for academics to have families, and to spend a very good amount of time with their families over the holidays and at many other times.
Put differently: there are some valid reasons why a person may not want to go into academia, but this isn't one of them.
Now, getting back to your actual question: is it normal for people in academia to work too hard, at the expense of time with their families? Well, it is indeed somewhat common, at least in the U.S. But this is by no means unique to academia; it is also common in the U.S. for people in many other industries and occupations to work too hard. The fact remains that there are many many people, both in academia and outside it, who manage to lead a very successful and productive professional life while maintaining a healthy balance between their personal and professional lives. Your sister's situation sounds rather extreme and unhealthy to me. Deadlines are a common (though not universal) feature of academic life, but usually one knows a long time in advance that a deadline is approaching, and for most people it is not too difficult to plan ahead and finish a project sufficiently in advance of a deadline to make allowance for things like holidays, family reunions, or any other commitments or plans. If your sister isn't doing this, I can think of several possible explanations:
Your sister is a young researcher who still hasn't polished her skills of managing a complex schedule. She will improve with time.
Your sister is the kind of person who is most productive under the pressure of a deadline. She may also improve with time as she finds that such things interfere with her personal life, or she may remain like this indefinitely.
Your sister has poor relations with you and/or other members of your family, and simply prefers to do work (or to pretend to do work) during family gatherings.
While some of these possibilities are indeed troubling, and you have my sympathy for the frustration that this is causing you, they are unique to your particular family situation and are by no means indicative of a general trend in academia. As I said, academia is a big place and you will certainly find in it all sorts of people leading all sorts of lifestyles, both healthy and unhealthy. If you are considering going into academia, I would advise you to make the choice based on whether you feel that this is the right decision for you given the lifestyle that you plan to live, and to not consider the examples of your sister and your father to be representative of anything.