How do you search for ownership title in the deed for real estate property located in NYC?

I am very confuse. If someone can answer my question, I am really appreciate. My mom & uncle bought a house together 7 years ago and they took out a 15 yrs mortgage together. 7 years later, my uncle told my mom that he just took a second mortgage for the house. Can my uncle do that? get a second loan w/o needing my mom to sign for anything. My uncle told my mom that when they took out the first mortgage, they already signed to consent so that they can take out second loan on the house if needed be. Is there really such thing? This really makes me question if my mom's name is even on the deed? Is there anyway to find out who has the ownership of the house w/o my uncle knowing? We can't really ask my uncle to see the deed because this will hurt the relationship between us. He will think that we don't trust him. Can someone please give me some advise?