There are several older posts on the same...one was a man who found his wife where she & her first husband taped themselves during their marriage, found in "packed & old items" in the garage. He put the tape in the VCR & found himself incredibly aroused. Search the site you may find a few & show that; no, you are not "odd" or "weird".
Acting upon it; that is something you would need to communicate well and be clear about; look through the pro/cons of threesomes in the threads.
http://www.sexinfo101.com/forum/marr...hree-some.html