To be honest, I’m not fond of her boyfriend. Sadly, my dad likes him a lot as he feels that he reminds him of his young days. I am older to my sis and not yet married or found anyone.
You don’t like your sister’s guy and are not too fond of him. But who is telling you to love him in the first place? He is your sibling’s choice, not yours. You have to be cordial and be supportive of her choice. It looks like you are most unhappy in the given situation. Is it because she has found someone and you have not? It appears to be that case. Moreover your father, too, is happy about it. So why are you being the spoilsport? I am sure your folks have done an adequate check on his background and found him to be a suitable match for your sister.