Simone Martini was an influential Italian artist who lived from 1284-1344. Although he was not as impactful as Duccio, he did an incredible job of popularizing Sienese paintings after him.
He impacted many, for example the local artists who imitated him in their paintings. It is assumed that Martini learned how to paint from the colour and figure styles that Duccio initially had painted with.
Comparing the two artist’s work, I notice that the faces and figures are very similar looking; however, Martini has added decorative lines and an extra elegance and beauty to his art.
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His paintings from Siena were a very important aspect of Late Gothic artworks, as the Sienese people knew Martini to have painted the first nonreligious Sienese painting, which was a portrait of Guidoriccio da Fogliano on a horse.
It is no doubt that Martini created a number of iconic artworks and influenced many.
Taken from: http://travelingintuscany.com/art/simonemartini.htm and https://www.britannica.com/biography/Simone-Martini