How do I [19M] deal with Mom who craves attention from elder son [21M]?

My mom wants my elder brother to love her back. I'm 19, he's 21. Since he's the elder child, obviously my mom loves him; she loves both of us. And I love my mom back too. We're both in college rn, so we're mostly away from home, but we come back for a few days here and there for holidays. I try my best to come home whenever I can. And when I do, I don't use my phone or laptop or do anything much. I try to spend most of my time with my mom, cuz I love her and I want to spend time with her. And though that makes her happy at least a bit, I guess, more often than not she's still sad because my elder brother is not giving her time. Whenever we're both at home, my elder brother will just stay on his phone almost 24hrs a day. He doesn't care about anyone in the family, nor does he have many friends. He's just a phone addict. He won't give my mom any time at all. She practically begs him to talk to her but he just won't. He'll keep using his phone watching reels or YouTube. For context, he's in a pretty bad college too and got a terrible placement. Career-wise he's fcked; his placement is so bad he won't even be able to make ends meet on his own without our parents' money. He's fcked in all senses. And still, he doesn't care, just watches reels and YT 24 hours a day. But my main point is, I come home hoping that I'll have a good time with mom and dad, but that doesn't happen because mom, rather than being happy that I'm spending time with her, is more worried and sad that my brother isn't doing the same. And however much she may scold or beg him, he stays the same. In the very few days I'm able to come home, most of the time is spent with my mom trying to convince my brother to talk to her and others in the house, sometimes begging and other times scolding. This makes me feel like not coming home at all. I can't just stop coming home entirely; my mom feels lonely with both children in different cities, and I genuinely want to spend time with her. But when I do come home, this happens. How do I deal with this? TL;DR: I [19M] visit home from college to spend quality time with my mom, but she spends the whole time sad and begging for attention from my older brother [21M], who ignores her to be on his phone 24/7. It's draining and makes me not want to visit home anymore. How do I address this with her and set better boundaries for my visits?