Did the Buddha ever mentioned what is the cause for having lovers / marriage?

I know there are clear explanations of cause and effect for things like the 5 precepts whereby; Killing is the cause for short live, stealing is the cause for being poor etc... But did our Lord Buddha or in any Sutta mentioned what is the cause for having romantic partners / marriage? Why do some people have lots of relationship, gets married and able to establish a family at a young age while some people might doesn't even have a lover? This is aside from worldly conditions such as being good looking or rich. We all have seen some people whom might not be good looking or rich but was always attached while the good looking and rich lived a lonely life. I'm not asking is it due to sexual misconduct whereby a relationship is broken due to adultery etc but rather the cause (Karma) for having a partner. Thank you.