Yes. I double checked with both contacts and screenshotted the conversation and both confirmed the attachments were not from them.
I think the question is related more to whether or not they actually sent the message vs the message with an attachment. If they actually sent you the message and in a previous comment you confirmed that it was part of a group conversation. This adds up to being innocent. Allow me to explain.
There are two ways to send group messages. They can be sent as individual messages and would send as SMS. SMS is a format we're all familiar with 140 characters no emojis, no pics or attachments. The second way is as MMS. MMS messages can include emojis and other types of attachments, pics, short vids, links so on and so on. Also with MMS group messages, typically, everyone who replies responds to everyone in the group message, so if Bill sends a message to Jane and Rob and Rob responds Jane and Bill both will see the reply. MMS is sent as a data packet and depending on a few factors, the recipient's carrier signal strength in a location, the network connection at the time of receipt and some times the size of the packet the data packet may or may not fully download. When the packet doesn't download or fully download a link is often sent so that the recipient can recover the message when conditions improve. When the person is back on their home network, in a better coverage area or when they have a stronger signal. The link is merely a placeholder if you will and a way to recover the message if not fully received. A lot of times if this is a one on one conversation you'll see this if a pic was included, where the text may be sent but the attachment is held until released by the link. Since group messages can be sent as MMS this can happen to them as well. So the real question is where were you when you received the these messages? Did you have a good signal, where you roaming on another network or where you moving where you may have been handed off from one tower to another? Anything like that, because it doesn't sound like you were sent anything nefarious but rather a link so that you could recover the MMS message if not fully received.
B. Diddy is correct, if it were something attempting to install something on your device you would have to agree to the installation, you would likely have to have Unknown Sources enabled because it wouldn't be from the Play Store and there would likely be other indications of an install, like a progress bar in your notifications. Email attachments from a PC is where we get this idea of things installing on their own because unlike an Android device a PC requires almost no permissions to install something and even bits of code in an attachment that is opened can have bugs that install. Links in messaging apps will usually try to open your browser and take you to a site that may be fake and try to get you to sign-up for something or sign in to your account for whatever fake it tries to be so that they can phish for your information. If the link didn't take you anywhere online, open anything in your browser and the message was one from a group conversation I'd say there's nothing to fear.
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