An idiom or phrase that means "as an act of solidarity"?

Question

I remember there was an expression like that used informally, but I can't quite remember what it was. I remember expression like "to scratch each other's back", but it's not quite that that I am looking for and it's something you can plug into almost any sentence and that always sounds good like "to one up one another". It's not "in solidarity", it sounds way too formal. I think it implied that they would get something back like the expression "to scratch each other's back", but it's ok if your idiom doesn't imply that.

For example:

Seeing he was drowning from fatigue, his brothers all flocked to him in order to ___.

Answer 1

One can say "to back up each other" or less formally but perhaps more vividly "he has my back". (The image here is of two people fighting back to back against a group of opponents, so that neither can be attacked from the rear.)

One could say "support each other" or in your sentence "support him" but that is more formal, less vivid, and not an idiom.

The idiom "one hand washes the other" implies "If you do something for me, I'll do something for you". It is also a bit out of date. Similar in meaning is "You scratch my back, i'll scratch yours" suggesting some sort of exchange of favors. But neither seems to quite fit the context in the question.