A Sunni brother asked in regards to verse 33:33 in Quran about the Ahlulbayt, he said;

Shia uses the hadith Al-Kisa to prove that Ahlulbayt is only Ali Fatima Hasan and Hussian. But they disagree with it. According to them, Ahlulbayt consists of 14 people.

They say that verse 33:33 is about Fatima Ali Hasan and Hussian. And they think the verse is proof that they are infallible.

My question is, if the verse is about 4 people. What about the remaining 9 imams, how are they infallible if the hadith and verse only deal with 4 people?

All matters relating to the verse including your question are answered in this lecture https://youtu.be/svJwsS2ZWJQ
Starts at 17:00 min