The previous title in the Bethesda Games, Skyrim, introduced the romance system to players. In the Hearthfire DLC, you could marry a companion from 67 choices (men and women) and then adopt kids. However, the marriage system has changed considerably in Starfield. Only four romances are available in the game, limiting the number of spouses you can have in your gameplay. The facility to adopt kids in Starfield is also different.
Understanding adopting kids in Starfield
The adoption system in Starfield seems to be rather vague at the moment. All we know for now is that there are hints of the facility to adopt kids in Starfield. Remember that there is no guarantee that we will be able to adopt kids besides romancing our partners. These are just hopes and assumptions from the early released concept art of the game.
You can be a kid yourself
We know that Starfield allows you to become a kid yourself, ready to be adopted by parents. You can choose the Kid Stuff Trait from the optional traits list. Then, you can visit your parents right after meeting the Constellation and completing the One Small Step quest.
After finishing the aforementioned quest, you can go to Pioneer Tower. This tower is situated in the Residential District of New Atlantis. Inside the tower, you will find an elevator that will take you to your family apartment. That’s where your parents will be eagerly waiting to meet their beloved (adopted) kid.
Aside from that, you cannot adopt kids in Starfield as of the game’s current state. Chances are that Bethesda will release a DLC later on, as they did with Skyrim, and offer family functionality separately.