All in the Family

SM09: All in the Family is a side mission in Deus Ex: Mankind Divided. It is available for Adam Jensen to complete during his second visit to Prague, assuming you completed SM04: The Calibrator by making a deal with Otar Botkoveli AND during M7: The Rucker Extraction you dealt with Louis Gallois by sparing or killing him.

Completing this mission will unlock the secret achievement/trophy of the same name.

Walkthrough
Upon returning to Prague, Otar will contact Jensen and ask him to visit Máša Kadlek, manager of the Red Queen. This will originally show up as a Point of Interest, One Last Favor before you talk and accept the mission from Máša.

Long story short, Máša wants her son, Dominik, to be married off to strengthen her connections but he wants to sit at the kingpin's table with Radich Nikoladze. As she cannot send any of her thugs into rival Dvali territory because of politics, she will task Jensen with abducting him without raising an alarm and gives him a photo to identify Dominik, who has a giant star tattoo below his left ear.

Dominik is staying at one of Radich's safehouses, Hotel Narikala. To infiltrate the safehouse, proceed to the alley behind the Irish Stool. Either hack the gate or jump over the adjoining wall, then climb the ladder and jump to the balcony on the left.

Once inside, make your way upstairs to apartment 95. A button on the TV stand will open a secret door on the opposite wall. Hack or use a multitool on the computer to turn off all security equipment.

Descend to the ground floor and deal with the thugs in the courtyard. Dominik will be found in the adjacent laundry room. Knock him out and drag Dominik up to the rightmost apartment on the second floor, preferably after having dealt with the two thugs inside, bring him over to the poker room's balcony then down to street level via the scissor lift to avoid him falling to his death. Open the unlocked storage unit and place Dominik inside, then closing the unit's door will complete the mission and net the achievement.