Galveston County sheriff's Capt. Barry Cook says the 23-year-old woman suffered first- and second-degree burns to her neck, face and chest on Thursday in Santa Fe.
Cook told The Associated Press that the brother is expected to face an aggravated assault charge. An affidavit has been filed but a warrant had yet to be issued Tuesday.
The woman contacted the sheriff's office, asking that the charge be dismissed but the warrant remains valid, Cook told the Galveston County Daily News.
Some pecan pie heated in a microwave allegedly was thrown on her. She required medical attention.
Cook says deputies were called after the woman and her brother apparently argued over their respective children. Cook says the woman told her sibling that their parents were too old to be watching both sets of children at the same time.