No, Ranbir Kapoor is not a Sindhi. He is a Kashmiri Pandit from the Kapoor family, a prominent lineage in the Indian film industry.
While his mother, Neetu Singh, is a Punjabi, his father, Rishi Kapoor, was a Kashmiri Pandit. The Kapoor family has roots in Peshawar, Pakistan, which was part of India before partition.
The Kapoor family has a rich history in Indian cinema, and Ranbir Kapoor has continued the legacy, establishing himself as a successful actor.