<human>: Can you provide a brief overview of the text?

My boyfriend is 16M

Three weeks ago my boyfriend was over at my house and we got a little touchy with each other. He just got back from the doctor after getting his stitches out in his arm. He did not really feel like having full blown sex he told me he was really tired. I persuaded him to let me give him a blowjob which did not take much convincing. 

My mother was at work and my sister in law was suppose to come over and watch us. As ridiculous as it sounds I am not allowed home by myself for a full day. She was suppose to come over at 3 in the afternoon so we had some time. Unfortunately she came over way earlier and we did not hear her. 

She let herself in and she saw me giving her brother a blowjob. She dropped what she was holding and she started to leave the house. He went after her but she told him to leave her alone.  

I mean really if we are being serious for a moment, as disgusting as is it is to think about she probably gives my brother them all the time. So What's the big deal in me giving her brother/my boyfriend one. 

My brother won't talk to me because I have upset her, My boyfriend is speaking to her but she 100% blames me even though I did nothing wrong. What do I do about this?
<bot>: SIL walked in on me giving my boyfriend/her brother a blowjob. Now my brother/her husband won't speak to me