Excellent answers. It may seem confusing/overwhelming to students of English at first. But if one pays attention, over time it gets much much easier. Believe me!

It depends on the context of the situation or conversation. Looking at a photograph, someone points to your father in the picture you should say, "Yes, he's my father" or "Yes, that's my father" but not "It's my father" If a guest is at your house and you are sitting in the living room, and someone walks in and you see that it is your father, and the guest says "Who is here?" or "Who was that?" then you would say, "It's my father."

You can use both. When you are introducing him in his presence you better say: "It's my father" If you are talking about him, when he is absent you rather say: "He is my father."

It depends what question you are answering. 1. Who's this? It's my father. when you introduce someone you always use "this": This is my father. He's the President of the United States. ...or.... This is the President of the United States. He's my father. You'll work it out.

Thanks to all. I hope my trying English will be good. I'll go on learning.