Doja Cat is allegedly being physically and verbally abused by her big brother ... at least that's what their mother is telling a judge.

According to new legal docs, obtained by TMZ Hip Hop, Doja's mom, Deborah Elizabeth Sawyer, filed for a temporary restraining order against her 30-year-old son, Raman Dalithando Dlamini ... and in her filing, she makes some serious accusations.

Doja's mom lists Doja as another person who needs protection from Raman ... reason being that Mama claims Doja had her teeth knocked out by Raman.

That's not all ... Doja's mom also alleges Raman has given Doja cuts and bruises, and destroyed and stolen some of Doja's property.

In the docs, Doja's mother claims Raman is also verbally abusive toward his famous sister "in a very degrading and demeaning manner [sic]” ... and she says Raman has made Doja feel "unsafe and traumatized."

As for her safety, Doja's mom alleges Raman physically abused her and threatened her multiple times over the past year, claiming the most recent incident happened earlier this month.

The judge granted Doja's mom court-ordered protection from Raman pending a hearing for a permanent restraining order but did not grant that same protection for Doja Cat -- instead, saying the artist would need to file her request for a restraining order.

It's worth noting ... Doja's mom says she had a restraining order against her son in the past, but it's since expired.

We reached out to Doja's rep ... so far no word back.