After Bianca, the royal doctor offered an unfortunate news that Oliver's health didn't allow him to get pregnant ever again. It was near a miracle how smooth his first pregnancy was and they couldn't guarantee the same thing for the second. Only if that would happen, which was nearly impossible.
Oliver was crestfallen, he had been looking forward to giving his Alpha lots of children, or at least he wanted to give Bianca a little brother or little sister to play with.
It took Lu Yizhou some effort on his part to convince Oliver that he didn't need anything else. That their little family was already more than perfect. Oliver seemed to register the comfort but Lu Yizhou still often caught him daydreaming as he packed up Bianca's little socks and bib that she couldn't wear anymore.
Lu Yizhou had no choice but to recruit some help.