Responses
I can agree with the marriage part since it was kind of rushed but for the baby, Kyungsoo wanted one. He's the one who encouraged Chowon to have one. It is clearly stated that Chowon asked Kyungsoo for consent before having a child. (Chapter 111)
Girl, have you read the last chap? Chowon asked him first about the baby, and about the wedding, he already know what was getting into.
I feel bad for the beta actually he doesn't deserve that messed up situation he was pushed to get married and have a kid which is not his just because the omega wants it