Throwaway because I don't want to risk anyone seeing this post on my main.

Now before I start, I'd like to say that I know that this is going to seem a little bit similar to [that episode of HIMYM], but believe me, I wish my situation was as comical as that one. 

Here's a bit of background- My mother was an only child with three kids, dad left after I, the third one, was born (though if I'm being honest I'm not even certain if we all have the same dad, she never liked to talk about our dad). Grandparents dead, no contact with any other family members. Me, my two brothers, and her are the extent of the family.

So let me start this off by saying that my mother is dying. She has probably a month to live, and that's being hopeful. I'm not going to bother going into the details, and if I'm being quite honest, I'm not 100% sure of all of them. Apparently it's common for patients with it to have heart attacks or strokes, and after she had one stroke she asked that if she had another one to not help her and let her go. I'm not certain if the hospital is allowed to do that, but that was her request (the reason I'm not sure of all the details is because I'm not at the hospital with her. My older brother stays with her, and me and my other brother try to make it to any important news sharing from the doctor. 

When we were younger, my mother always said she wanted to see all of us settle down and start a family with someone we loved, so we could have what she never got to. Both of my older brothers succeeded and made her happy with that, but I have not. However, I have been in an extremely casual relationship for the past year. I'm talking basically a FWB type thing but slightly more serious. We've gone out on dates with other people in that time with no jealousy, but if either of us ever wanted to maybe make things more serious, we'd be open to the possibility of it. I've brought her home to holidays and such at home, but my mom is aware of how casual we are. 

So with my mother's wish she always expressed when we were younger, and the current... situation, I've been considering telling my mom that my "girlfriend" and I are engaged, so that she can die at least thinking I'm on my way to creating the life she always wanted for me. When I told my brothers my idea, they had different responses. The oldest said I was an asshole for even considering manipulating our mother, but the other understands where I'm coming from and would be okay with me doing it, even if he wouldn't do it if he was in my situation. I also talked to my "girlfriend" and she said she would do it if I thought it was for the best. I'm just worried that if I do my oldest brother will think I'm an asshole and resent me for it, and honestly I'm not too sure if it's the best idea myself.

So Reddit, WIBTA?