Helena and Sergey were already thinking of having a second child when Sergey found Worf in the rubble of his home on Khitomer. Helena agreed to take Worf in once Sergey explained that Worf had nowhere to go to and that he might be in danger within the Klingon Empire. (TLE novel: The Art of the Impossible)
Shortly after the death of K'Ehleyr in 2367, Worf sent their son Alexander to live with Helena and Sergey on Earth. The following year Helena took Alexander with her to meet Worf on board the USS Enterprise. She explained to Worf that she and Sergey were getting older and that they weren't able to properly care for Alexander and that he needed to be with his father. When Worf objected Helena stated that Alexander was having behavioral problems on Earth and needed guidance from his father.
At that Worf relented and allowed Alexander to live with him for the next three years until the destruction of the Enterprise-D in 2371. Following the destruction of the Enterprise-D Alexander returned to Earth and moved in with Helena and Sergey. While Worf thought Alexander was happier living with them, Alexander resented having been left behind by his father. Eventually Alexander left to enlist in the Klingon Defense Force in 2374, at the height of the Dominion War. (TNG movie: Generations, TNG episode: "New Ground", and DS9 episodes: "The Way of the Warrior", "Sons and Daughters")
Being a close friend of Worf, Jeremy Aster also met Helena and Sergey and befriended them. Whenever Aster visited Helena would not allow him to leave their home without ensuring that he had a good meal first. (TNG novel: Diplomatic Implausibility)