Home Sweet Home (2020)

Blurb:
The last thing Jungyeon expected was for his mom to ask if she could remarry. The new man was kind, considerate, a perfect match for his mother but there’s a catch: he has a younger son. Sunwoo is an introvert. He’s shy and has trouble opening up to others, until he meets Jungyeon and finds himself opening up for the first time. As their parents get closer to marrying, they become close, too close, and that’s when Sunwoo learns Jungyeon is already seeing another man.

Source: www.anisearch.com/manga/44701