1. Who is Melchizedek?
All we know about Melchizedek is that he was the king of Salem and priest of the Most High God. Abraham met him on his way home from a military victory and they broke bread togather. Abraham gave him a tenth of his spoils (a prefiguring of the tithe concept). This is all recorded in Genesis 14:18-20.
2. Is He the type of Christ(the Messiah)?
Yes, since Jesus is the true King of Peace (Salem) and our Great High Priest in the heavenlies.
3. Who is (was) His Father? Who is (was) His mother?
Hebrews 7:3 states that Mechizedek was 'without father, without mother.' Perhaps this means he was an angelic being. Perhaps he was a theophany. The Bible doesn't tell us much about this interesting man (if indeed he can be said to be a man).