Healthy family relationships pay attention to the principle of "Fond or Favor." It is a way to help the family system stay healthy. It helps the family system get on a better path. 

Most importantly, it is best when the father and the mother have a 3+ relationship.

Favor means the father has a 2+ relationship with the son(s), and the mother has a 2+ relationship with the daughter(s). When “favor” is used, it does not mean they are to care more for them but to help the children look more like their God-given design. Boys look like, even mimic, godly men, and girls look like or mimic godly women.

On the other hand, we want the father to be fond of the daughter and the mother to be fond of the son, which is a 1+ relationship instead of a 2+ relationship.

Fond or Favor respects the idea that God designed the mother to teach the daughter(s) feminine types of things. And the father is better equipped to teach a son masculine-type things than the mother.

With that in mind, what is the role of the opposite-sex parent? What do they focus on teaching opposite-sex children?

Maybe the most critical skill or principle a mother needs to teach a daughter is how to respect, depend on, and trust a godly man. You do not want to teach girls that all men are untrustworthy – certainly, many are. But a healthy family system starts with God’s design, not what Satan and the world say. And at the same time, teach them how to recognize a respectable, dependable godly man.

Maybe this is the most important part! What does that imply about the mother? She believes in and does those things. She models that behavior with her husband. Additionally, she teaches her daughter how to be a godly woman when the husband ISN’T respectable and dependable!

Now what would a father need to teach a daughter? What a respectable, trustworthy man looks like and what protection looks like. Of course, this goes completely against the current, politically correct, world portrayal of women being powerful. That is not how God designed His system. A woman is not supposed to have to protect herself. Men are designed to protect women. A father teaches a daughter to look for that type of guy.

Again, this implies that the father is modelling that godly behavior!

Cultures have certain issues to consider, but do not let culture diminish the clear system God has ordained for the marriage and family.

Then, on the other hand, what is a mother to teach sons? What a respecting, trusting, depending godly woman looks like. “Son, here is the type of woman that respects and trusts godly men. Watch how I do this with your father. Watch how I respect him in both the good and bad times. That is the type of woman that I want you to be looking for in the future, a woman that has inner beauty.”

And what does a father teach his son? Obviously, how to be a respectable, dependable, trustworthy godly man. How to protect a woman.

Those are the basics of the fond-or-favor issue that is going on. 

Without that system in place, there is an easy path to cross-gender triangling.