I Don't Think My Sister's New Boyfriend Is Good Enough For Her, Should I Tell Her?

Being someone who has gone through this before I would recommend pretend niceness, it depends how much she cares about him and how far into the relationship they are.  Just be there to listen to her when she calls and give light suggestions or recommendations.  Chances are he could try to isolate her from her family if you tell her what you think and she tells him.  Play it safe, tell her you support whatever decision she makes even if you don't agree with it and that you love her and care about her but you just want her to be happy with whatever decision she makes...it sucks listening when you want to say what you really think about that stupid jerk loser dude, but trust me...you're better off not doing it!  Keep in contact, give her a call weekly just to see how she's doing.....

We all feel the need to protect our family and our friends from things and people which we think are bad for them, but sometimes we have to let them deal with it on their own.

Your sister has obviously seen something in this man which is special, or she wouldn't be with him. You probably haven't seen him in the same light. I'm sure when you meet he feels under the spotlight and pressured. You may need to take a little time and effort to get to know him.

I would suggest that unless he has done or doing anything horrible or potentially hurtful then you shouldn't say anything. If your sister asks if you like him, just say your not sure, but once you get to know him better you're sure you will.

The only other thing you can do for her is be there for her if it goes wrong and prevent her from making decisions which she could regret.

I think that you have to let your sister decide for herself whether or not her boyfriend is good enough for her.
You might find that your sister resents you if you interfere on this one even if you are trying to do your best for her.

You are kind to care about her but until you know more about her boyfriend and how they get on together you are much better letting them get on with their relationship.
We often are tempted to give opinions when we are trying to help or we care for someone but these opinions aren't always appreciated and I think this is one of those instances when she may not welcome your opinion.
If there is something wrong with him I'm sure she'll find out soon enough and then you can take the opportunity to tell her how you feel but not just yet.

I just think you should tell your sister whatever you feel. Nothing wrong with that, isn't that what sisters are supposed to do? It won't move the earth. Its just a conversation of hearts between you two. Say all you
want to and just tell, here. Its just your feeling and it could be wrong,
But you thought it right to tell her. I believe she'll take it to heart, and it'll be appreciated. Its always helpful, when a family member cares enough to give their Thoughts. Communication is a priceless gift.

I think that you should talk to your sister and ask her if she's happy with her boyfriend. If she is then its best to leave it that way because it's her happiness that matters first. If you have seen or observed something in her boyfriend in particular that you think is not good for her, then maybe you should try to draw her attention to it. Her reaction is unpredictable, but the way you say whatever it is that you have noticed will make a difference.

Whatever you decide to do, make sure it doesn't hurt your sister's feelings because a family bond is more important then any other.

Good luck!