I found out Me and my brother are only half siblings because of cilantro

So me(18) and my brother(21) were having a conversation about dinner and during i brought putting cilantro in the food and he said that he doesn’t like cilantro. because it taste like soap and I remembered learning in school that this is a gene .that can be passed to your kids and that it was a gene you were most likely to get from your parents i brought up to my mom who shut down completely and wouldn’t say anything so I decided to go behind his and her back and Order dna test and turns out my brother dad is some guy that mom was with on break from my dad.I showed the papers to him showing the only half match between us and he didn’t care.but we confronted my mom with the papers and told us we broke her trust and that it doesn’t matter if we’re half siblings and now she will not speak to me. I don’t care that we are half siblings i only did the test because of the way she acted I didn’t expect this from cilantro.