BIL Text Me In Error-he is having an affair?

[Robertsmithsnan]

I sent my BIL a message last week, my name starts with R.
Received a message at 7am, “R, you are the light of my life, I love you with all my heart”
He sent this to me by mistake.
The “R” person is someone he works with. What do I do?

Not sure how the OP has so
much detail on the other woman and what they have got up to

If he was my husband, I would. It's fine if you wouldn't want to.

Infidelity is abuse at every level: mental, emotional, sexual, physical (STDs), and above all financial. OP's sister is a stay at home wife in her 40s-60s. She's in a HORRENDOUS position financially because she trusted this man.

If I was in her shoes, the gloves would be OFF.

Yes, unlikely that it's not gone physical. Also unlikely that the woman doesn't want him, as he claims. Cheaters always tell a monumental pack of lies at the beginning and often they stick to those lies for years, or they trickle truth relentessly, driving their poor spouse completely mad.

If he deleted all his messages, he's lying and your sister can't trust a word he says. It's likely a physical affair that's been ongoing, that's why he deleted his messages.

You really did the right thing here.