Do all parties on home deed need to be there in order to change names?

I'm writing this for my dad who just found out that he has been paying on this house he lives in with brother and sister in law and their 3 kids, himself and his sister. In 1972 when they bought the house, my dad was the only one with enough credit and money to buy this house for their family. Well in 1983 my dad moved to Los Angeles California. He came back to Maryland in 1985 because his mother had died and all this time he was still making payment on a home. So he goes back to California and came back here to Maryland to stay and live. In 1997 and my step dad was going to change the names around well when he looked at deed he noticed that his family had already made many changes that he would have never done. My dad was paying for this house all the way up till 2000 or so. Anyway he told his sister who was indeed that he wanted to take his name out but then a few days later his sister comes back saying she can't do it. So he figured that his name was still there will finally in 2004 he somehow got his hands on deed for like a day and we looked it over and there were many bad things in there for me but I'm no lawyer. They were changing the names all around and his brother that never lived in that house when they first bought but somehow is name is there along with his sister. Somehow by this time, we say that they have taken my dad completely off and I have no idea on how they could have done that. So I'm sure there are some very shady things they don't want out but I feel it’s my fathers right to his portion of that house he put more money in it than all of them the house was only 79,990 in 1972. He put 30,000 cash down and was making double payments all the time so they could get paid off. Well eventually the house does get paid in 1999 and my father still didn't see anything.