Should I Tell Her?

Last night I was included in a group conversation text message (I really hate these).  There were about about 10 of us (all couples who have been friends for years), everyone chatting and I was just reading them as the phone dinged about every minute or two.  After a while I decided to respond to what someone had said, no big deal!

About an hour later, I get a message from a number that I don't recognize that says "Who is this?" My daughter had used my phone just before this,; so, I asked her if she had called someone or dialed a wrong number by any chance and she said she had not.  So... I'm wondering who this could be because I haven't ever see the number, and was not about to tell them who I was (lol).  After a few minutes I responded to the message and asked, "Who is this?"

Then they replied "My name is ****".  For the sake of privacy, lets call him Robb!  I'm sitting there thinking and I only know one "Robb" and I don't have his number and I know for a fact he doesn't know mine; so, this must be a random stranger who thinks he is talking to someone else!!  So, I asked him How he got my number!?  A few short minutes pass and I get another message, this time he doesn't respond to my question but a
sked if I am on this site that I have never heard of...

So, I go online and research this site... which happens to be a site that people sell sex on and where they are expecting human trafficking!  My thoughts were "Oh my gosh, I don't think so!!"  Who is this guy and how in the hell did he get my phone number?!

Before I can respond and tell this creep not to ever text my phone again, he responds again and asked what my name is!  Then, another message goes off, but in the group chat... which is from this same number!  So I send a message to my friend who started the chat and asked who the number belonged to?  She tells me it's "Robb".

I was telling my husband what was going on and who it was, and how he must have gotten the message I sent in the group and somehow mistaken me for someone else.  Needless to say, my husband was getting a little frustrated with the situation, as I was as well.  Then my phone went off again, another message from "Robb" asking this time if I would send him a picture!  Seriously!!??

OMGosh... he is messaging me thinking I am someone else who is on a sex site; yet, he is married and has kids with another friend of mine!  WTF!?

My husband gets the # and messages him, telling him that he should watch who he is talking to and asking for pictures... He replies, "Who is this?"  My husband then tells him who he is and that he has been messaging me!!  Not but a few seconds pass and he gets 3 messages explaining how sorry he is, then I get an apology message as well.   Then my husband tells him that what he's doing is very disrespectful and he's sure that his wife wouldn't like it, but we wouldn't say anything THIS TIME!

BUT I just can't get over the fact that he was trying to hook up with someone and he has a wife & kids... However, this isn't the first time he's done things like that to her; but the first time I have been involved and I want to tell her because I would want to know if I were in her shoes!!!

However, in the many years they have been married it seems like two to three times a year he has cheated, left her for weeks to be with other women, and has admitted to numerous  women as well.. Therefore, I don't think telling her would make any difference, do you?  I can't see how someone could put up with that crap, but I'm not in her shoes!

Regardless of all that she had put up with and kept going back to I still feel the need to tell her, but Should I tell her?