
It's because their children are twins I thought sumi got pregnant by his previous (alpha) pair. He did mention he's in love with his twin brother so the twin genes must've been from him. But I don't wanna be the bearer of bad news so I'll just presume that the kids are really actually from the beta dude.

WTH sumi twins Both are Beta like Utou and he is the father just wait for chapter 15 translation release, they conceive the kids when meet Utou family.
https://asukanon.tumblr.com/post/635772181998174208/utousumi-babie-twins-rei-boy-and-shizuku

I didn't out myself, just got caught by my friend during my weekend date. When school came, gossips and meaningful look started coming my way. I was ostracized although in a gradual manner. They must've thought I'd start looking at them differently. Gosh! Not all gays grab on all dicks. Get real! And they aren't even a looker. Didn't bother explaining myself and just let the friendship fade. Good riddance!
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Ahh, this is the best time to apply what the uke did in TEN YEARS I LOVED YOU THE MOST. Go on a trip. Take the time loving yourself. Regroup. Forgive. Forget. Move on.