I am a Marathi speaker from central India but I wouldn't call myself Marathi ethnicity because the term is too broad. My family is from the borderlands of Marathi culture and we are like a 1000km away from Marathi culture heartlands.
The region in India I am from is extremely diverse with 4 major language speakers living side by side, it was also a famous internationally well connected kingdom centuries ago and there were migrants from all over the old world.
Genetically, no idea. Probably a good mix of Aryan (not the European definition) and Dravidian. If I had to guess, ancestors on my father's side were Dravidian speakers who adopted Marathi a long time ago. On my mother's side, ancestors were probably gifted lands in the region or they simply migrated southwards from northern India looking for new lands.