To be annoyed partner is prioritising his brother over us on holiday

Yes, bad idea to have a holiday with the brother as well as 2 toddlers. I think you’ll just have to suck up the fact that DP will be mainly be focussing on his DB this trip and not you/your kids. He’s probably making up for lost time. In future, he should go away with him alone for a long weekend or something.

Yes he is but he's being reactive to a very understandably clingy younger brother.

Perhaps in future, your DH could take him away for a weekend so it's just the two of them and you can have your family holiday separately?

He needs family, that’s why. He’s craving it because he doesn’t have it. Every time your partner is hands on with the kids, all he will feel is that he doesn’t have that in his life (but he won’t actually be aware that that’s what he’s feeling - he’ll just act on the impulse to have that attention).

Your partner needs to start turning to him and saying, “I hear you, but I also have a baby to care for and I cannot just stop. Come sit down by me while we do this.”
He also needs to challenge the boy’s comments of “you always do this” because it isn’t true, and it’s ok to sit down and talk to him about that. Tell him that he is paying attention, he is putting him first on lots of occasions but he cannot drop everything all the time and he cannot ignore the little ones just because X is shouting his name over and over.

You need to understand that this boy doesn’t mean it maliciously and won’t even understand why he is doing it. But it’s ok to have a conversation.

When he starts shouting for attention and your partner is with the kids, what are you doing? Are you saying things like, “I’m here X, show me what you’ve seen” etc? You need to acknowledge and involve him. It’s hard work, but you’ve chosen a partner from a difficult background with a younger brother who needs this sort of help so… you need to give it.

Does he ever live with you? Time away from placement to live with family?

I think you might have to resign yourself to doing two totally separate holidays from the same accommodation - you and the toddlers, DH and his brother.

Don't even try to do things together, and don't try to take his brother over so DH can take the twins because it's only one week (if he was moving in permanently this would be something you would need to do).

It's absolutely classic disordered attachment to try to push his attachment figure away in order to test him - everyone your teenage brother in law has trusted has failed him (in his mind - quite possibly there have been fantastic teachers and care givers in the children's home, but his parents and foster placements have effectively abandoned him - although it's highly likely the foster placement had no choice if there were other children resident).

If your husband is serious about being his stable adult then you need to let brother in law have him during the day this week.

It may be in future that it's better for your husband to see his brother 1:1 until his brother understands he's not going to be rejected or initiates seeing his small nephew/s/ niece/s.

He won't be emotionally 14 (regardless of intelligence - it's completely separate) because of what he's experienced - emotionally he's probably a toddler himself in some ways and he has the same type of emotional need for his parent-figure's attention as a toddler. Essentially he's a toddler and a teenager both at once and he can only help that to a limited degree.

I have worked with kids in this position and what your husband is doing is really life changing if he does it well, but you need to help him by stepping away and single parenting the toddlers while your husband is with his brother.

Eventually you should be able to do things together, but he needs to feel secure first and it could be a couple of years off.

Yeah I agree with the other posters. Your partner is in a tough spot here. It sounds tough all round but I don't think that there is an easy answer here. Everyone is just trying to do their best having been dealt a shitty hand.

I would never go on holiday again with him. Why don’t you tell him to be patient when he is doing this? You have the right to. Also I would just keep a closer eye on the little ones. He’s troubled and seems very competitive with young children and might so I would just watch out.

He obviously is prioritising his brother. I don't know that there's much else he can do at this point though. He's an adult who's chosen to take responsibility for a very troubled child for a week, that means doing what's necessary. The time to have a problem with this has passed,

But it's perfectly fine if you don't want to go on holiday with the pair of them again in future.

This.

I get it’s tough but this child is just trying to build a bond with probably the only person who shows him some love.

can you try to spend some time with him so your partner can spend some Time with the twins? Or get him involved in helping with them. Make him feel loved and part of the family

His db sounds a troubled dc. Your toddlers are thankfully part of a loving family. Easy to understand why the teen may be feeling a bit envious..
You need to make him feel part of your family also and he may relax and cheer up.

What do you want your DP to do at this point?