John Constantine, a character with multiple offspring, had a child with a demon named Rosacarnis. Unfortunately, Maria Constantine, John's daughter with Rosacarnis, has been missing since a significant event where she displayed no will to live. Given the emphasis on John's past and his current decline in the new series, it is probable that Maria will reappear. Here's an image of John Constantine and his daughter Maria: 
John Constantine is facing his own mortality, which puts his daughter Maria, who happens to be a demon, in danger. This means that Maria is likely to make a dramatic comeback and reunite with her half-brother.
In the comic book series "John Constantine: Hellblazer - Dead in America #1," it is revealed that John has had numerous love interests throughout his long history, some of which resulted in children. One of his children is Tefé Holland, the daughter of Swamp Thing. Additionally, John had three children with the demon Rosacarnis: Adam, Saul, and Maria. However, Maria has been largely forgotten until now.
In a previous storyline, when John's life was at stake, he struck a deal with Rosacarnis to save himself. The deal required John to spend a single day with her. However, due to clever wording, this "day" turned out to be three entire lifetimes within a dream world. During this time, John raised Rosacarnis' demonic offspring, which included Adam, Saul, and Maria.
Rosacarnis believed that demons raised by John would possess his knowledge and become unstoppable. Hence, Adam, Saul, and Maria were born as a result of this demonic bargain.
The comic book "John Constantine: Hellblazer - Dead in America #1" (released in 2024) is written by Simon Spurrier, illustrated by Aaron Campbell, colored by Jordie Bellaire, and lettered by Aditya Bidikar. The cover art is also done by Aaron Campbell. This series has been highly acclaimed, being regarded as DC's best ongoing comic run due to its captivating and visually stunning storytelling.
It is revealed that Maria Constantine, John's daughter, is the product of a demonic pact and represents his darkest nightmares in Britain.
Rosacarnis had created each of her children in a dream world where John had stayed with a prominent love interest. Maria, one of her children, was raised by John and Angie Spatchcock in Liverpool while England was collapsing into nationalism and bigotry. Maria had a specialization in ritualized magic and was secretly sacrificing vulnerable people with her friends. After leaving her dream reality, Maria targeted Constantine's friends and family but ultimately found no joy in existence. The First of the Fallen killed Adam and Saul but let Maria live because she had no desire to survive. However, Maria has never been seen since that climactic moment.
It was part of Rosacarnis' deal with Constantine that if John died, Maria and his other children would die too. With John slowly decaying, it would make sense for Maria to appear and play the situation to her advantage. The new series has been focusing on small details from John's history, and the fact that he has a missing daughter is not something that the creative team would overlook. Therefore, it's highly likely that Maria might make a return.
Simon Spurrier and Aaron Campbell's time with Constantine has invested in his lore, and hopefully, John Constantine's forgotten daughter is due for a return. The mystic's strange living death would directly concern her, and with a good reason to show fans what happened to Maria and a creative team who knows Hellblazer inside out, it would be exciting to see her return.