Johavah question...PLEASE ANSWER?

so i just found out that jehovah witnesses where only established in the 19th century. in all seriousness, and no rudeness meant...how excatly do yall think that something that came out hundreds of years after christianity was set is even true...also how do yall feel about mormons? again this is a serious question for knowledge reasons. also if yall use the christian bible, where do yall get your beliefs?