Cernd's Companion Quest - Baldur's Gate 2
Cernd's Companion Quest is called Cernd's Child and begins when you enter Waukeen's Promenade with him in your party. Upon entering Waukeen's Promenade Cernd will bump into an old neighbor named Igarol who will mention that Cernd's previous wife had a child after he left to answer his call to nature.
For the first part of this quest you'll have to visit Cernd's Former Home which is marked on your map in Waukeen's Promenade. Inside you'll find someone named Catis who will tell Cernd to go speak with his former servant and Nanny, Fennecia. You can find Fennecia inside of her house in Waukeen's Promenade which will also be marked on your map.
In order to have Fennecia open up to you, you'll have to remove Cernd from the house. With Cernd outside Fennecia will tell you that Cernd's child is at the Deril Estate in the Government District. You can find the Deril Estate in the southeastern portion of the Government District - like most other locations during this quest it will be marked on your map.
When you arrive at the Deril Estate you'll meet his golem butler who will have some dialogue with you before he fetches his master. There will be a short conversation with Deril before you're faced with the choices shown in my screenshot above. If you encourage Cernd to face Deril alone he'll get killed and you can not resurrect him, he'll be dead permanently. Telling Cernd "all is lost" will result in him attacking Deril as well for the same outcome.
The only dialogue options that you'll want to choose involve attacking Deril together as a group or putting pressure on Deril to hand the baby over. You can get the baby from Deril without a fight but that means you'll lose out on the EXP for killing Deril (and his friends) - so the choice is yours.
Once Cernd has taken the baby from Deril he'll tell you that he is leaving the party and taking his child to the Druid Grove map. The quest will technically complete at this time and the next time you visit the Druid Grove you'll find Cernd waiting for you inside the stronghold here. You can recruit Cernd back into your party at the Druid Grove and like the good father he's been thus far, he'll leave his child in someone else's care yet again.