I think that Sanji was cast out of the Vinsmoke Family/Germa66. I also want to believe he left, but I just want to talk about this.
Sanji’s trademark curly eyebrows are very noticeable.
After the timeskip his hairstyle switched over to his other eye, revealing his other eyebrow.
I believe that Sanji’s eyebrows are the reason he may have been cast out of the Vinsmoke Family/Germa66.
In the new One Piece Chapter a new character of Germa66 has been revealed. He has the same eyebrows as Sanji but flipped around.
I believe the of Germa66 is named that because of the trademark eyebrows of the Vinsmoke Family that look like 6’s.
I believe Sanji was cast out because he was born with eyebrows that don’t look like 6’s but to them deformed and didn’t represent Germa66,
and so the Vinsmoke Family/Germa66 cast him out.
Thank you if you have read this.
*Theory by Strawhat Joseph
He left. Reasons
1. The family makes his wanted poster to be Only Alive (Meaning they want him or he holds importance to the family, if they do not want him (in ur theory > cast him out = ashamed of him), they should left him die so that no one will know that he is related to Germa66 and they would not be ashamed anymore).
2. They arranged him to marry pudding = an important marriage to form link with BM.
Germa means brothers
i think he ran away for some reason.