I feel horrible

Story time:

Three years ago, when I was a fresher, I thought a guy in my dept. liked me because of how he used to act around me. Eventually, he found out and told me that I was misguided for thinking the same…we became best friends nonetheless. Three months later, his best friend at the time told me that he DID like me and lied to me about it :)

By that point, he and I were talking about another girl he had a crush on, so naturally, I thought that he had moved on and proceeded to be friends with him(without letting him know that I knew about his feelings) The reason why he will never mention his feelings is because it will ruin the friendship but most importantly, he and I belong to different castes (and my family is extremely casteist)

A year ago, he got into a serious long-distance relationship with someone. But during this year, he has flirted with me a lot to the point of saying that what if (hypothetically) a guy loved u to the point of pretending to be of your caste ? Would you consider marriage then?

I feel bad for his gf but i don’t know what to do…is this even cheating on his side?