Responses
Nope, it was more along the lines that they weren't "perfect". He specifically sought out a powerful cold type for his wife because the weakness of his fire type was overheating. He wanted a perfect child with both fire and cold who could use their power without limit by continuously cooling/heating. It's not that they were weak, they just didn't have that balance so I think the reference was them as "failed experiments". I don't remember which episode it was, sorry.
The other kids are just like their parents, Todoroki's just the mixed breed here.
Question, was it ever explicitly stated that the Todaroki children other than Shouto are weak?