Torn between 2 sons

Have you ever heard that song "Torn between 2 lovers?" Well, I kind of feel that way. I told my Mom that she was lucky to have an only child. That she didn't have to deal with squabbles between 2 children. Now I'm use to Alan and Rick fighting but, this one is by far the worst. Alan calls Rick, hen pecked, that's not exactly what he calls him but it means the same. Barb, Rick's girlfriend in opinion will tell Rick to jump and Rick will ask how hi.
Rick has taken care of Barb and her daughter Makayla. He buys all their food, Makayla's diapers and rent on 2 rooms. He has now taken out a loan for $3000 for a credit card bill that Barb had outstanding. Her Mom was going to do it but also had 2 mortgages out and felt she couldn't do it. But my son could? I'm proud of Rick for being responsible, but the loan I don't understand. He couldn't have traded in his truck and gotten a loan for a better, newer car. Now, that is on hold at least for 2 years. I'm concerned for the stress that he is under and stress and MS do not get along.
Rick calls Alan a pig. Alan has never picked up after himself very well, he is disorganized, Rick knows all this it has never changed. But now suddenly he's a pig.
Alan has always been Rick's biggest supporter and visa versa. So the thing that has changed is Barb. The things Rick has been saying are coming straight out of Barb's mouth.
So what is a Mother to do.....tell them to mend their fences.