The others pretty much got it right. I'm almost 50 and at this age, feel strange calling my partner my "boyfriend". So, I came up with the term Partner in Mischief because we have lots of mischievous adventures together!
I'm reading a novel with my PIM (partner in mischief) titled The Mandibles, by Lionel Shriver. I was thinking that the novel may have been written recently because so much of it reminds me of our current economic & political situation, but I was very surprised to learn it was originally written in 2016! It's eerie how much the author has gotten right!