https://old.reddit.com/r/asktrp/comments/3nu470/my_older_sister_is_cheating_on_her_bb_fiancé/

This is an alt account made for this post. While I have a main account I cant have it associated with this subreddit.

I am 22 y/o living at home currently at University.

My 26 y/o sister who has a lot of debt, never has any money and will most likely be living at home indefinitely. She has no real career and doesn't earn a lot. Yet my parents allow it without any real motivation to improve her situation.

I recently found out that she has cheated on her fiancé (at least once), and it resulted in her having an abortion (Unprotected sex).

Her fiancé is quiet/shy and well mannered. Has a good job/career and is looking to settle down with my sister, he is 26 and has a mortgage.

My sister has one thing on her side, she is in good shape and attractive (gets plenty of attention.)

They have been dating 3 years.

Should I tell him and if so how would you tell him?

I'll admit that I resent my sister: how she acts and just floats through life never having to work hard for anything, and for this reason cant really make an unbiased decision. Looking for advice.