Don't be fooled by their nerdy appearance, if you mess with their son, Saiki and Kuboyasu will fuck you up.

Take that one Terusai art but make it Kubosai instead and suddenly the height difference actually works

By surface level alone, Kuboyasu and Kusuo aren't too different. Both hold onto secrets regarding their past, though each of them have differing degrees of success with it. I certainly wouldn't question Kusuo if he wound up with Kuboyasu, that ex-delinquent can be sensible in plenty of cases, and I'm sure Kusuo has the capacity to handle his temper when he can't restrain it. Actually, I believe Kuboyasu would be able to assist Kusuo with opening up a bit more. From what I've heard, he has explained his past to a couple people, just like Kusuo has! It is also reassuring to know that Kuboyasu would be able to protect Kusuo, should anything go awry. That's not to say Kusuo is incapable of protecting himself! I simply mean he shouldn't have to fend for himself all alone whenever he gets into trouble. I suppose I can summarize that, since I did get a bit more in depth than the question asked. Kubosai, as you called it, has my approval!

These two can barely catch a break. Hopefully now that Yuu is a toddler she's a bit more self sufficient and they can get some time to themselves.