Thomas was largely a self-taught painter with some help from his older brother Edward. However, he was not the only one in the Moran family who painted. His eldest brother Edward Moran (1829 – 1901), was a noted marine and historical painter who had studied with James Hamilton. Hamilton’s style was similar to that of English colorist J.M.W. Turner whose work subsequently made an indelible impression on Thomas Moran.
Peter Moran (1841 — 1914), etcher and painter, was well-known as an animal painter and etcher. Peter was taught by his older brothers Edward and Thomas. He traveled to the West in 1864 and he toured the West with Thomas in 1879. Peter's wife Emily Kelley Moran (1841 – 1903), from Dublin, was also an artist. John Moran (1831 – 1902) was a landscape and architectural photographer in Philadelphia in the 1860s and 1870s. He was the official photographer on the Selfridge expedition to Panama.
Mary Nimmo Moran (1842-1899), Thomas' wife, was a native of Scotland who was landscape painter and highly recognized American landscape etcher. She was the first woman fellow elected to the Royal Society of Painter-Etchers.