I have a theory on this:
If you feel stabile in your life and within yourself, you are more likely to look for someone similar to you.
When you lack inner balance, opposites attract more strongly hoping to gain balance by dating someone not similar to you.
You may also say that this depends on how you feel about yourself.
Agree or disagree?
I have dated both and was married to 2 women, both of which were RH negative and with both we had RH negative children. I”m currently married to an RH positive lady but no children. It should be noted my mother and biological father were both RH negative and had 5 RH Negative children. When my mother remarried it was to an RH positive man and they had one son who was RH positive and nearly died at birth. My oldest daughter is A– and the man she married is B–, and all 3 of their children are AB–. Matings with RH negative people seems to be the norm in my family. At the moment, I’m the only person I know of in my family with an RH positive person and been married 23 years.