It's a power play. He is withholding his love from you in order to get you to "beg him back". It makes him feel powerful. When you drop the rope and say "maybe it's for the best" that's when he starts up with the "I love you" stuff in order to gain control back.

It's sad, but people like this can't maintain healthy relationships. Regardless of whether or not you keep him in your life, you need to understand this.

Now that I’m thinking about it maybe it is better just to let the relationship go. It’s just not really worth the stress. It’s sad to say but it’s very similar to my mom, where it is just a one sided relationship on their terms. I have a lot of really great friendships, that make the lack of family support better. I don’t want to just hold onto this relationship and deal with the stress of the ups and downs.

This is his self-healing mechanism. It's ok - you can accept that. Just let him know that you will be there for him when he reappears.

Hugs OP.

OP, you sound like a female. You cannot & will not change his behavior. Dont allow him to be rude or manipulative just to have him in your life.

Yes, like you said it’s all about him. A perfect example of this is him being upset after his birthday saying I didn’t reach out to him to wish him a happy birthday. (we are twins)

Drop the rope. “Family” only goes so far. Either people treat you fairly, with respect, and with care, or they don’t. I’m sorry, because you deserve better from family, and I know it must be tough to see other families that are more functional (but still imperfect).

If he’s around, try to enjoy his company. If he’s not around or threatens to not be around, let him go do what he needs and wants to do. His behavior is not your responsibility, and not within your power.

Your power is that if you want to enjoy him when he’s behaving decently, you can. And if he’s acting toxic or treating you poorly, YOU can disengage and set some boundaries.

You don’t have to dance to his tune.

This sounds like all about him and his mental illness - is he borderline?

Backstory: We come from a very broken family. Father + only only sibling passed away tragically and suddenly. Mother is narcissistic/severely mentally ill and toxic.

When things are going great for my brother, he’s involved and when things aren’t he will literally block me and disappear for a year. He was almost engaged to a woman he was dating for 2-3 years and they broke up and he disappeared. He’s always wanted a very certain life (family, good job, money) and he’s living a different one (single, lower paid job, roommates). It’s really my only immediate family member. I also have kids, young ones though, so they wouldn’t notice if he disappears. He’s also mean about it sometimes. I’ve always begged him back, for lack of better word but the last time he was being rude (he was telling me he had visited my city twice -he’s a part time flight attendant- and he didn’t even care to make an effort to see us.. which is actually fine but why say it?) He was also threatening to block again. He threatens weird things like he’s taking me off his will. This is strange because we are the same age. I sort of dished it back and “that’s fine.. I don’t know what to say. Maybe it is for the best.” Then he changes his tune and is like “I love you, blablabla” ... I guess I just don’t need the drama but don’t really know how to handle it because he’s my only immediate family member that’s alive, aside from my non who is in a home.