Alize Yasmine Mendez, 16, and Xavier Alfonso Mendez, 15, have both been missing since April 16 and were seen in the 900 block of Baker Drive.
Police say Alize, who goes by Zay, has been seen since she left, but her brother has not.
Alize was wearing a black shirt, black pants and black Nike Air Force 1 shoes. She wears her hair straight, wavy or sometimes in a bun. She has long hair that hits a little past the middle of her back. Alize has her ears and belly button pierced.
Alize is described as a Hispanic female, 5'2", 120 pounds with brown hair and brown eyes.
Xavier was wearing black sweats and a black shirt. He has brown eyes, wavy hair and pierced ears. He is described as a Hispanic male, 5'1" - 5'2," and weighs 130 - 140 pounds.
According to police, both siblings went to Alief Taylor High School, where Alize was in the 10th grade and Xavier was in the 9th.
The siblings' family is concerned for their safety.
If you see them or have information, you're asked to contact Sergeant Smith at 281-290-1315.
Police now believe the siblings could be in the Houston, Fort Bend, Alief, Cypress, Katy, Bear Creek, or Aldine areas.