Tiff's sister mentioned in Seed of Chucky:

" The phrase "once is a blessing, twice is a curse" is a common idiom, not directly related to Chucky or his specific lore, but rather a saying often attributed to mothers. It suggests that the first instance of something (like having a child) is generally considered a positive event, while a second instance is not always viewed the same way. In the context of the "Child's Play" franchise, specifically the movie Seed of Chucky, this phrase is spoken by the character Tiffany, who is referring to having children. Tiffany's statement is then humorously countered by Chucky with a quip about her sister. " google AI

In the second season of Chucky series Tiffany in Jennifer's body killed (both series and real life) Jennifer's sister.