But i heard from my friend, her gynae told her, some men sperms are more biased, as in more of boy or gal sperms, dont know why, could be genetic or the things they eat. Then in those cases, no matter how you ML, whether close to O or not, you will always get back the same gender. That explains why some family, 4 kids and all same gender.
Waa, imagine having all boys then next time must wash their army uniforms till siao ah?! PP, xin ku ni le!