It is very obvious that the guy is just there to mess up you and ur sisters life, and U cased it bcos, u'r not too careful. So, Just let him go
U are 29 for God's sake, u need to allow God to settle you, u can only try, but it only God that can settle you.
Therefore, move very very close to God (Give you life to Christ - Be born again), is not yet too late, God can still give you the best, and He will.
Don't forget to also warn your sister of the future implication of her action.

God av mercy, is getting 2 much in this country!