Is it normal that my bil dislike their brother

Ive been with my partner for about 10 years we met in high school he has no sister its only 4 brothers (ages 26 married w 3 kids R, 22 married with 1 child A, 21 just married no children I & last one is 10 still in school E) (including him is 5 he's 29 we have 2 children) Ive seen it all & ive heared it all as well. Most of the time i like to speak my mind and which most of the time they disagree with me. Ive been in verbal fights with two of my sil because of rumers they have said of me. I know for fact that the R wife has always hated me (evil two face bia) xxx so over time Ive tried making peace with theirs wifes (R&A) & they pretend to like me but then they turn on me xxxx so ive seen the difference in how the 3 younger brother R,A&I have distance them selfs from their other brother xxx they dont Communicate like they should. In which we have both noticed that but we don't like to bring it up sometimes & talk about it. I really dont like to tell my mil nothing beacuse she takes her other kids side of the story (& the fa t that we all live close by) xxx i really dont know how to do it sometimes or how he stays so strong knowing how they treat him differently. Out of all the older brother hes always by his dad side helping him around the ranch (I & My husband) buying things that his other brothers wont do for their dad. For some reason i believe his dad in some way dislike his own son.. Xxxx