SOLVED. YA Dystopian Fantasy, read in 1995-1998. Girl and boy are trapped by evil queen in the future after apocalypse, she raises them in a "castle". Title similar to "Children of Time". [s]

[Tammy]

the cover had a woman's face with red flowing hair. Yellow cover

She grooms the boy and his sister as part of a new human race after the world becomes extinct, they are separated from their father who is a scientist. She drugs the boy by giving him heavily spiced food, there is a part where he tries to keep himself awake my rubbing a cut or wound..

I swore the book was called Children of Time, but that is the title of another book, so it must be something similar

[Rainbowheart]

Children of Time

[Tammy]

Omg thank you so much Rainbowheart!!!! I’ve been looking for this for so long and for some reason only Adrian Tchaikovsky’s Children of Time showed up!!! Ahhhhh!

[Rainbowheart]

You're super welcome, glad to help out!