looking for a good kdrama/jdrama where husband or wife has a secret child 

or a drama where mother or father is getting out of jail and seeing there kid after so long

✔️ Old Boy (Chinese) 

✔️ Oh the Mysterious ( 2 secret kids) 

✔️ Moorim School 

✔️ Mirror of the Witch 

Hateful but once again

  • Empress Ki
  • Moon Lovers Scarlet Heart Ryeo

Probably not what you're looking for, but here are also some dramas where the female lead is reunited with a parent when she is a young adult after they were separated from them or assumed they abandoned them or died when she was a child:

  • Healer
  • Love in the Moonlight

not really with the leads being a married couple...f but still one of the leads realize or find out they have a child belatedly...

  • Marry me Now (Ongoing)
  • Mama
  • Only You
  • My Love Eundong

Let me Introduce Her | currently ongoing.