Sorry, but the twins method didn't work out in my experiment.. I still believe the twins are random.

No twins at all throughout the experiment, just single babies.. I tried:
- Cologne on wife, Perfume on husband, boost on husband
- Perfume on wife, Cologne on husband, boost on wife
- Cologne on wife, Perfume on husband, boost on wife
- Perfume on wife, Cologne on husband, boost on husband
I did this with a fresh family and used backups to undo the child they had to use the 4 different methods I listed. I think you're just lucky with the multiples!

Congrats on your good fortune, cindy!