Blood ties.

After that, Kevin asked Gavin to sit on the chair in front of Kevin's desk.

  "Papa is going to work for a while, do you want to wait while playing a game?"  Kevin asked in a soft voice.

  Gavin nodded with a smile.

  After that Kevin continued his work seriously after wearing minus glasses.

  A few moments later.

  "Papa..." Gavin was getting bored because Kevin hadn't finished with his work yet.

  "What is it?"  Kevin asked without looking at Gavin.

  "Mama ... "

  Kevin stopped his work when he heard Gavin mention the word Mama.  For the first time, Kevin heard the word from Gavin's adorable little mouth.

  "Mama?"  Kevin asked while looking at Gavin in surprise.

  Gavin nodded.

  "What do you mean?"  Kevin was still confused because he couldn't guess what Gavin was thinking.

  "I miss Mama! So, Papa call Mama now!"  Gavin explained to Kevin what he meant without mentioning who he called Mama.