They are on the witness list, yes. On that basis, the defense asked - and was granted - for them to be kept out of the courtroom until they testify, asserting that what they heard might influence their later testimony. (In court, they simply refer to such a request as "invoking The Rule" with no further explanation. If you're on the receiving end of such a maneuver and don't know what it means, it can be quite confusing. Families tend to get pissed, if not prepared for the possibility.) That's the one and only way close family of the victim can be kept out of the courtroom at the start, as Texas law mandates that they otherwise be allowed to be there, and even if they are going to be witnesses a judge can rule that he doesn't think it will be a problem and opt to allow them to stay, because they are close family. Texas courts are intended to be as victim friendly as possible.
Later, they could be removed if they create a disturbance of some sort, but since the trial hadn't begun, that was not and could not have been part of the equation. The defense requested, the judge saw it as a legit issue, and he ruled accordingly.