I think we can predict a couple's child's mbti even if the kid is not born yet.

I have this theory since I notice a pattern lately. If you are an INTP, you will likely have one of the parent who is also an INTP or ESFJ or ENTJ. Why 3 these types. INTP is ESFJ but just have same function backwards and INTP is shadow of ENTJ.

Similarly, If you are an INTP, If you have a kid in the future, they can potentially be an ENTJ, INTP or ESFJ

If you are an ENTP, you will have a ISFJ (opposite), INTJ (shadow), or an ENTP kid.

If you are an INFP, you will have a ESTJ (opposite), ENFJ (shadow), or an INFP kid.

If you are an INFJ, you will have a ESTP (opposite), ENFP (shadow), or an INFJ kid.

If you are an INTJ, you will have an ESFP (opposite), ENTP (shadow), or an INTJ kid.

Although most INxJ I know are pretty anti-procreation. They won't likely have children while it's opposite to INTP who likely will give birth because it feels nature to them.

If you are an INTP and date an ENFJ for example, your kid will be INTP, ESFJ, ENTJ, ENFJ, INFP, ISTP.

So that's my theory.