I kept hearing about being able to have mixed gender twins or triplets so I decided to try it out in my game. It really works.
All I did was:
-Make both parents have the fertility treatment (more likely to have triplets)
-Had a doctor in my active family determine gender of the baby when she was 'showing' (doctor must be level 5 in medical)
-They said she was having a girl so I made her eat three apples (and nothing else throughout the whole pregnancy, used cheat code '
testingcheatsenabled true' to help)
-Then when she had the babies, she had a girl and two boys.
Hope this helps
If it says she will have a boy eat three watermelons.