hvszk:
in Ep.1 Sung Ji Eun had convo with the other lady who also did the same psychopath DNA test, she told SJE that it's her 23rd week of pregnancy, meanwhile SJE was in her third trimester (I assume) that is between 28th-40th weeks based on what Dr. Lee said to SJE "you're past the stage where it's possible for you to get an abortion"
in Ep.4 when Yo Han accessed JBR medical record, we can see that JBR was born on May 25th 1995
in Ep.6 when Moo Chi accessed Ji Eun data at police station, we can see that Yo Han was born on January 26th 1995
based on the pregnant distance and birth distance, i still think that YoHan is indeed HH's son
But what if they are swapped after Jae hoon killed his family? a difference of three months would mean nothing if they were swapped at that time. And also we don't get any clue about JBR and Yo Han's past during that time (elementary school and junior high school).