Q: Did the Prophet sallallahu alaihi wa sallam have other siblings?
A: It is recorded in Al Khasaa'isul Kubraa (V1 P73) of Allaamah Suyuti (Rahmatullaahi Alayh) that his mother did not give birth to anyone besides him, i.e. Rasulullah (Sallallaahu Alayhi wa Sallam).
Allah Ta'aala knows best.
Moulana Yusuf Laher