Why do Sara & Ibrahim Ali Khan not have "Pataudi" in their last name but Taimur does?

Something I noticed was that Sara & Ibrahim's last names are "Ali Khan", so Sara Ali Khan & Ibrahim Ali Khan, and these are their names on wikipedia and when you look them up on google etc. But with Taimur, when you look him up, his official full name is "Taimur Ali Khan Pataudi". Why the difference? All 3 are Saifs kids and born into the Pataudi family. I don't think it's because he isn't married to Amrita Singh anymore because he is obviously still Sara & Ibrahims father. But its like they are only acknowledging Taimur as the "heir" to Pataudi or something.. do you guys think our very own Bebo had anything to do with that?