A nine-week-old baby was one of five people killed in a house fire in Sheffield, along with two women and two other children.
A cousin of one of the women said the other two children were aged nine and seven.
He said the two women who died were his 54-year-old cousin and her 20-year-old daughter - the children's aunt.
More top news
The chancellor now faces the prospect of forming a minority government or calling for a snap election.
The 73-year-old said a return is unlikely "given the politicised atmosphere that seems to have afflicted our set."
Chancellor Philip Hammond said the UK will make a financial proposal to the EU in the next three-and-a-half weeks.