has he worked with any of his family member?
His sister Caroline and his son John.
William Herschel
Caroline spent many hours polishing the mirrors of high performance telescopes so that the amount of light captured was maximized. She also copied astronomical catalogues and other publications for William. After William accepted the office of King's Astronomer to George III, Caroline became his constant assistant.

who discovered titania? William Herschel. which planet does it orbit? Uranus. how did it originate? It might have formed from an accretion disc or subnebula; a disc of gas and dust that either existed around Uranus for some time after its formation or was created by the giant impact that most likely gave Uranus its large obliquity. what is the atmosphere of the planet you mentioned? The outermost part of Uranus's gaseous envelope that is accessible to remote sensing is called its atmosphere. does it have moons? Yes, it has 27 known natural satellites. can you name some of them? The five main satellites are Miranda, Ariel, Umbriel, Titania, and Oberon. has herschel made any other discoveries? He discovered two moons of Saturn, and Uranus. He also  measured the axial tilt of Mars and discovered that the martian ice caps changed size with that planet's seasons.
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William Herschel [SEP] Works with his sister Caroline
Following the death of their father, William suggested that Caroline join him in Bath, England. In 1772, Caroline was first introduced to astronomy by her brother. Caroline spent many hours polishing the mirrors of high performance telescopes so that the amount of light captured was maximized. She also copied astronomical catalogues and other publications for William. After William accepted the office of King's Astronomer to George III, Caroline became his constant assistant. In October 1783, a new 20-foot telescope came into service for William. During this time, William was attempting to observe and then record all of the observations. He had to run inside and let his eyes readjust to the artificial light before he could record anything, and then he would have to wait until his eyes were adjusted to the dark before he could observe again.