Keep the relationship platonic!

I have two characters who normally would be set as romantic interests. Instead, I'm giving them more of a brotherly-sisterly love (these are the two main characters). I'm still early on in the story, so I'm not having a lot of trouble yet, but I'm struggling with how to make them seem like they've got a sibling love instead of a romantic love without having them saying "He's like a brother to me!" (because I hate when people use it, it's a bit unoriginal) If anyone has any ideas on how I could make it work, please let me know! :)