How do I deal with my younger brother being so disrespectful towards me?

It sounds like he may be hurting that you have a whole new life that he doesn't really figure in. He may feel forgotten. If he felt more like your son in the past, then imagine him coming home and not being the most important person. Obviously, that's all figurative and I'm sure he's happy you're doing well, but some you and him time wouldn't go amiss. Say you want to spend a day//half a day with only him, then do it. Before he goes have a chat about how things have changed, but not your affection for him. Remember too he's a teenager so likely to be a bit moody

He might have felt completely abandoned by you if you left 5 hours away while he was calling you mom? He probably resent you for leaving and "replacing him" with your baby and got jealous. He needs you to connect with him.

Totally agree with what is said above, he’s obviously feeling hugely emotional about something, maybe things for them aren’t as rosy as they seem, he’s definitely hurting and needs you to press in and get him to open up and make him feel loved etc which may not happen straight away but as the adult you have to try

Just to clarify he hasn’t called me mum since he was 5. I moved out 6 years ago and my Lo is only a year and a half so I don’t think this has anything to do with me moving away and having a Lo, especially as i actually think I became even more closer with my family including my other brothers since having my Lo. His treated everyone as normal including my husband and child but has just been very nasty and making so unnecessary comments about me.

Being 14 years old is hard, and I think all teenagers deserve grace for that alone. Don’t take it personal as I’m sure his heart doesn’t really want to hurt you. I was a bitchy 14 year old for no reason, and have made some apologies for it as an adult. My sister is 8 years younger than me and started high school last year. We used to be really close but since I’ve moved out of the house and started my own family, she’s bitter anytime we’re around one another. We see each other like twice a year now so I understand why she wouldn’t feel connected anymore. While it hurts my feelings when she’s having an attitude with me, I let it go. As she gets older, I know her heart will be in a different place. My parents tell her to be nicer to me but I wish they didn’t, it probably enhances those negative feelings. As older siblings, we just have to love them where they’re at and remind them that they’re loved. I think your brother/ my sister may feel forgotten in a way.

I took care of my sister a lot when we lived together. And I know she relied on me for stability and as a role model. When I moved out and poured my life into my husband/ baby, I can only imagine how lost she felt. I’ll never know what it’s like to be the younger sibling but I try to empathize. I’d imagine it was a big life change for her sister to move out and not see her every day. She doesn’t like to open up to me so I don’t put pressure on her. But I do try to stay connected with her by randomly calling just to say “I love you” or send photos of my daughter to make her feel included in my life. At that age, it’s common to feel invisible. But from what I’ve learned in therapy, it’s the adult’s responsibility to step up in these types of relationships. Give him time and grace, that’s really what we all needed as an angsty teen.

Honestly sounds like a typical 14y old. Don’t take it too personally deep down he loves you obviously, he’s just in a « bad age »
Try to talk to him if you can, but if you don’t try really don’t take it too personal and keep give effort and treat him as if nothing happened. Try to have nice moment with him, to share something you know he’s gonna enjoy, or like do his favorite cake for example
Don’t be in revenge, or ignore him, he’s just in hormonal change, maybe he has issues at school or somewhere else, this age is tough and boys don’t speak about their issues…
Maybe also he just misses you and the life with you before, that’s his way to express it
This will go away soon don’t worry, just try to be his older sister you always have been, include him and keep doing an effort. Maybe will feel useless but it won’t, he sees you and will regret

I ve been a role model for my younger sister (5 years appart) her entire life. When I moved 8000 km away she never forgave me and our relationship is now practically ruined 9 years later... She never accepted me being far away (despite the fact I get back home at least twice a year ..). You don't have to feel guilty for making your own life but sometimes we have to accept other people can't accept our life choices...