Auntie issues

Okay so my brother and this girl we're a thing, it was kind of like a on and off but they both had feelings for each other. So my brother finally went off and found somebody that was like a real relationship. And then his girl he was hooking up with came back pregnant,

and they were together on the conception date. My brother has been denied this whole time but me and my mom are sitting here behind the girl and giving her so much support. My brother will not get a DNA test or do anything for the baby. The baby was finally born on November 4th 2018, and I have done everything for this kid. She has the most presents underneath my tree and my brother still will not do anything for her. Is there any way I can convince my brother that it's his kid. The baby looks exactly like him and has the same nose and many other features. please help!