Any idea why my SMS text messages containing links aren't being received by group chat participants?

So this is a weird thing I noticed recently: Whenever I send a group text to my siblings, if the text contains a link, they don't receive the text. But they can get my group texts without links, and they can get messages with links if I send only to one person.

Extra info: I use Android, and they both use iPhone. It's just so weird to me. Why only messages with a url? And why only with group chats?