Gregorio Martín Martín, who is best known under his pseudonym Grema, is a creator of illustrations and juvenile characters. Born in Toledo, his family moved to Valencia when he was six months old. Grema has spent his entire career living and working in this city. In the mid-1950s, he began drawing for the magazines of Editorial Valenciana. In the magazines Jaimito and Selecciones de Jaimito, he drew characters like 'Pancho Bigotes', 'Gasógeno Taxista', 'Piolet y Mosquetón', 'Pelé y Melé', 'Pepito Pegote' and 'Profesor Cabezolín'. In Pumby and Súper Pumby, his most famous character was 'Barbudín'.
Grema has illustrated books of 'Carrers y Racons de Valencia', with urban landscapes of the city. He has also drawn for the foreign market, collaborating with among others Yps and Rolf Kauka's Fix und Foxi in Germay, Sport Billy in England and 'Dr Snugles' in Holland.