Tex. Civil Practice and Remedies Code § 15.003

(a) In a suit in which there is more than one plaintiff, whether the plaintiffs are included by joinder, by intervention, because the lawsuit was begun by more than one plaintiff, or otherwise, each plaintiff must, independently of every other plaintiff, establish proper venue. If a plaintiff cannot independently establish proper venue, that plaintiff's part of the suit, including all of that plaintiff's claims and causes of action, must be transferred to a county of proper venue or dismissed, as is appropriate, unless that plaintiff, independently of every other plaintiff, establishes that:

(1) joinder of that plaintiff or intervention in the suit by that plaintiff is proper under the Texas Rules of Civil Procedure;

(2) maintaining venue as to that plaintiff in the county of suit does not unfairly prejudice another party to the suit;

(3) there is an essential need to have that plaintiff's claim tried in the county in which the suit is pending; and

(4) the county in which the suit is pending is a fair and convenient venue for that plaintiff and all persons against whom the suit is brought.

(b) An interlocutory appeal may be taken of a trial court's determination under Subsection (a) that:

(1) a plaintiff did or did not independently establish proper venue; or

(2) a plaintiff that did not independently establish proper venue did or did not establish the items prescribed by Subsections (a)(1)-(4).

(c) An interlocutory appeal permitted by Subsection (b) must be taken to the court of appeals district in which the trial court is located under the procedures established for interlocutory appeals, except that an interlocutory appeal from the business court must be taken to the Fifteenth Court of Appeals. The appeal may be taken by a party that is affected by the trial court's determination under Subsection (a). The court of appeals shall:

(1) determine whether the trial court's order is proper based on an independent determination from the record and not under either an abuse of discretion or substantial evidence standard; and

(2) render judgment not later than the 120th day after the date the appeal is perfected.

(d) An interlocutory appeal under Subsection (b) has the effect of staying the commencement of trial in the trial court pending resolution of the appeal.