Shia say they are the followers of ahlul-bayt, im curious how? As we know ahlul-sunnah claim the same thing.

Thats what i used to believe, but the truth is it is more than that. The most obvious difference is in there believe of imamah, its part of there aqida and any one who dont believe in this have deviated from islam(according to them), its alien concept to us(ahlul-sunnah). Then there is the believe of al-rajah that there imams will be resurrected before youmul qiyaama(that means they believe in two resurrections).

The third major difference is the belief in the invisible mehdi who supposedly went in hidings thousand year ago. And they say this mehdi guides them now and he is there current imam(leader)(much similar to christian holy spirit). And the fourth big difference is they believe that all companions of the prophet(saw)except few(max 9) became renegades and munafiqin after prophets(ra) death.

The fifth difference is they believe the quran was tampered. Altho majority of them now have abandoned this belief, but they still believe that todays quran is not in right order(verses misplaced). This is only few of the major differences and they are many.