Search Results: his ex confronted me

So I recently saw his ex posted a photo of them acting all cozy at a wedding together (the wedding has the exact date from last Sunday) and this raised my suspicion that there might be cheating going on… I asked him about it and he seemed honest but I’m not sure who to trust.

Would you consider these characteristics/things to be a sign of potential infidelity?

• Wasn’t defensive when confronted, willing to talk about it with me the entire night
• Gave me his social media passwords
• Gave me his phone to look through
• His mom told me that he was home Sunday morning and he spent the rest of the day (of the supposed wedding) with me
• Came over the next day because I asked to talk about this again, he listened and answered all questions
• Got pissed at his ex and completely sided with me, because she has a habit of posting old photos of them

Some red flags 🚩:

• The photo of the wedding has the date of last Sunday (but then why would he be willing to take photos with her knowing that she’ll post them online, and he knows I can see her posts)
• The wedding ceremony was held early morning to noon. His mom left his house at 11 and he only came to see me at 1:30 PM
• Her ex’s friends also reposted the photo on their accounts (but his ex used to post old photos of them acting as if they were still together)
• Last year he was caught still talking to his ex, but he has sinced changed and cut her off (from what he’s shown me the past year)

Imagine a situation where:
-Older Brother (30): In a committed relationship for 3-4 years, living with his girlfriend.
-Younger Brother (27): Had a tumultuous, on-again/off-again relationship with a woman (25) over the past year.
-The Ex-Girlfriend (25): Struggled with the relationship due to repeated cheating, emotional conflicts, and mistreatment by the younger brother

When the Ex-Girlfriend First Reached Out to the Older Brother, He Was Supportive and Neutral → Initially, he listened, gave neutral advice, and didn’t seem to have a strong opinion about her or the relationship.

-However, After That, the Older Brother Became Harsh & Judgmental → Over text, he started expressing strong dislike toward the ex-girlfriend, saying she was manipulative and toxic.
-The Older Brother Has Reached Out Multiple Times to Confront the Ex-Girlfriend → Instead of ignoring the situation, he actively engaged with her in texts, being dismissive and harshly critical of her role in the relationship.
-The Ex-Girlfriend Tried to Explain Her Side → She reached out to the older brother to show him the full picture, explaining that she had been hurt, cheated on, and mistreated. However, the older brother ignored this perspective and continued blaming her entirely for the toxic cycle.
-Even After the Breakup, the Older Brother Still Feels Strongly About the Situation → Despite the fact that the younger brother and the ex-girlfriend have broken up, the older brother continues to speak negatively about her and express strong feelings of resentment toward her.

What do you believe are the primary reasons for the older brother’s intense and harsh behavior toward his younger brother’s ex-girlfriend?